Question

If the sum of two expressions is 3x+5 and one expression is 5x-7 what is the other expression

Answer 1

-2x + 12

Explanation:

If we call our other expression y, we can set up an equation tying together 3x + 5, y, and 5x - 7:

`(5x-7)+y=3x+5`

Solving for y by subtracting 5x - 7 from both sides will get us the expression we're looking for:

`y=3x+5-(5x-7)\\y=3x+5-5x+7\\y=-2x+12`

So the other expression in the sum is -2x + 12.