Mathematics

Question

The sum of two numbers is nine if one number is subtracted from the other the result is -1 find the numbers

1 Answer

  • Lets make x and y the two numbers. The sum of the two numbers (x and y) is 9 means that they add to 9. So the first equation isĀ 

    x+y = 9

    Let's isolate y by subtracting x from both sides. That gives us

    y = 9-x

    The other bit of information given is "if one number is subtracted from the other, the result is -1", which means we have this other equation

    x-y = -1

    From here, substitute y for 9-x

    x-y = -1
    x-(y) = -1
    x-(9-x)=-1
    x-9+x=-1
    2x-9 = -1
    2x-9+9 = -1+9
    2x = 8
    2x/2 = 8/2
    x = 4

    If x = 4, then y is...
    y = 9-x
    y = 9-4
    y = 5

    Therefore, the two numbers are 4 and 5. They add to 9
    4+5 = 9
    and they subtract to -1
    4-5 = -1

    Final Answer: 4 and 5
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