Answer
$x=110$
Work Step by Step
1. This ratio is the short leg over the long leg for each of the two triangles. Don't forget that you need to do the same addition to get the long leg of the larger triangle
$\frac{50}{100}=\frac{x}{100+120}$
2.Solve to find the x:
$\frac{1}{2}=\frac{x}{220}$
$2x=220$
$x=110$