3x+4 is the average of 2x+2 and 8x-14 because it's exactly between the two on a trapezium. therefore: 3x+4=(2x+2 + 8x-14) / 2 ↓ 3x+4=(10x-12) / 2 ↓ 3x+4=5x-6 ↓ add 6 to both sides 3x+10=5x ↓ take away 3x from both sides 10=2x ↓ divide both sides by 2 5=x
