Question

There is a mistake in this equation, could someone help me find it please?

Answer 1

The mistake happens between the third and fourth equations, when they should ADD 6x to BOTH SIDES, but they added it to the left, and subtracted 6x from the right. Should be:
-6x + 10 = 4x + 20; now ADD 6x to both sides;
10 = 10x + 20; subtract 20 from both sides;
-10 = 10x; divide both sides by 10 to solve for x, so x = -1

Answer 2

`- 6x + 10 = 4x + 20 \\ - 6x - 4x + 10 = 20 \\ - 6x - 4x = 20 - 10 \\ - 10x = 10 \\ x = - 1`