Answer:
x=2
Explanation:
if m/A and m/B are equal, to find x, your equation would be 20x+10=30x-10. doing two step equations, you would substract 20x from both sides, making your equation look like 10=10x-10. then you would add 10 from both sides making your equation 20=10x. then you would divide 10x from both sides making x=2.