What does x equal in -10-5x-2x equals -3?

-10 -5x -2x = -3

Add 7x to both sides: -10 + 0x = 7x - 3 and then drop 0x

Add 3 to both sides: -7 = 7x

Divide both sides by 7: -1 = x

but you should just pay attention in school and you wouldn't need to ask this question.

try harder in school and don't be a fool.