x+4+2x-7=180; x 4 2x 7 0; find the sum of (5y−12)+(−5y−1).; find the difference of (t−8)−(t+15).; x-2=-3x+6+2x; 7x -(1 + 9x); -3 + 5x = 4x - 10; −3(3x−1)=8(3−x)