0.4(5x-12)+0.5x=15.2
We move all terms to the left:
0.4(5x-12)+0.5x-(15.2)=0
We add all the numbers together, and all the variables
0.5x+0.4(5x-12)-15.2=0
We multiply parentheses
0.5x+2x-4.8-15.2=0
We add all the numbers together, and all the variables
2.5x-20=0
We move all terms containing x to the left, all other terms to the right
2.5x=20
x=20/2.5
x=8