1.1x+1.2x-5.4=-10x
Move all terms to the left:
1.1x+1.2x-5.4-(-10x)=0
Add all the numbers together, and all the variables
2.3x-(-10x)-5.4=0
Get rid of parentheses
2.3x+10x-5.4=0
Add all the numbers together, and all the variables
12.3x-5.4=0
Move all terms containing x to the left, all other terms to the right
12.3x=5.4
x=5.4/12.3
x=3.8571428571429/8.7857142857143
Hope it helps!