What Is x and y?

Hello, Everyone! How  R U?

I want to give U a math problem, high school algebra or college freshman algera level.

Let x and y be two unknown variables.

Question : If

x+y=7

x-y=3,

then,

what is x and y?

Solution:

x=___

y=___

Hint: solve it as system of linear equations.

If  U have forgotten about this level of math, please think about the question by guess: how many ways to have two numbers sum as 7, then find the pair of numbers with difference as 3.

for example,  7=7+0=6+1=5+2=4+3=3+4=2+5=1+6=0+7, I have told you 8 ways of sum to 7.

Solutions: x=5, y=2.

check:

5+2=7,

5-2=3. Thus solution is correct.

There are many ways of doing it, Doraz commented exactly how to solve it graphically, mathematically, or using methods of substitutions, cancellations. We can also solve it using graphing Ti-83 calculator…Any way. I give this question which is mediate hard, thus I prefer not to make it too abstract to majority readers. Let me know if you have questions!

Outstanding job, everyone who joined the fun! 15 of U did wonderfully in math computation on this one.

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31 thoughts on “What Is x and y?

  1. x=5 and y=2

    Q: what is the sum of all the whole numbers from 1 to 100?

    A: well, there are 50 pairs in that range, and each pair = 101 (for example 1+100=101, 2+99=101, 3+98=101, etc.) So, the answer is: 50 pairs x 101=5050!

    thanks Jingle, talk to U later!

  2. x=5, y=2
    If you can believe it … We are now teaching an algebraic based math series and that would be one of our problems in … First Grade!
    Hard to teach 7 year old this concept … Hard for them to learn!

  3. ok Jingle my work is as fallows
    x+y=7
    x-y=3
    Lets start by adding x to both sides of the second equation.
    this means x=y+3
    after that you substitute this equation for y in the first equation
    this means that 2y+3=7
    from their you subtract 3 from both sides and devide by 2 giving the answer
    x=5
    y=2

    great problem Jingle. Thats what I’m doing in my math class.

  4. Ha! I think I got it! x=5 and y=2

    I thought that my bedrest had completely melted my brain, but apparently there is something small left in there, doing some work. 🙂

  5. Wow! You are one of those brilliant math-minded beings!!! I bow to You and smile and say my brain will explode if I dive into this. I’ve got a circus mind and numbers never got the memo to come on over and join in! I SO admire people like You! Thank YOu for the kindness You left in my room!!! Cheers and Namaste. 🙂

  6. Hi Jingle,

    Are you kidding with this???? LOL! This is one of the reasons why I chose art school!! I look at equations like this and I want to draw beautiful, fluid, calligraphic lines all over them. What is the answer, like a 2 or something? (Not that I tried to figure it out!!!) Love, Lisa

  7. The system has a unique solution:
    x = 5
    y = 2

    It can be found various ways
    -The point at which the two lines intersect
    -Creating an augmented matrix and using Gaussian elimination (row echelon form) or Gauss-Jordan elimination (reduced row echelon form)
    – Creating a Matrix A=[1,1;1-1], vector column b [7;3], then taking the inverse of A and multiplying it by vector column b.
    Note: to find the inverse of a matrix, take (1/determinant(A))*adjoint(A).

  8. x+y=7
    or, x=7-y
    Putting the value of x in the equation x-y=3 we get:
    7-y-y=3
    or, 7-2y=3
    or,-2y=-3-7
    or, -2y=-4
    or, y=2

    hence x=5 and y=2

    Am i r8 Jingle?

      1. I thought you were doing algrebra, not calculus or differential and stuff. Ugh. Sure, ‘splain it to me. I miss my dad enough to listen to another lesson. (He used to catch me on my way to watch a tv show and say, “Come here. Let me show this.” Of course, I missed the show.) 😀

  9. That last comment was intended for the poem you posted before this. My apologies.
    I am not a math fan, what so ever. My brain does not work that way.
    Happy Wednesday, almost Thursday to you!

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