Question

Find two numbers, if their sum is 115 and their difference is 7.

Answer 1

The answer would be 21 because,

x+y=115
x-y=21 x=y+21 now substitute (y+21) for xin the first equation.
(y+21)+y=115
y+y=115-21
2y=94
y=94/2
y=47 answer. no solve for x
x-47=21
x=47+21
x=68 answer.
proof
47+68=115
115=115

Answer 2

61 and 54

Explanation:

Let the 2 numbers be x and y. We can write this system of equations from the given information:

x + y = 115

x - y = 7

Adding these 2 equations gets rid of y (because y+(-y) is 0) and we are left with 2x = 122. Dividing by 2 (so that we can get rid of x's coefficient), we have x = 122 / 2 = 61. When we plug x = 61 into the second equation (you can plug it in to either equation), we have 61 - y = 7, and y = 54. Hope this helps!