Question 161283
This is a classic 3-4-5 triangle. ONe leg is 30, the hypotenuse is 50. So the other leg must be 40.

{{{50^2 = 30^2 + x^2}}}
{{{2500 - 900 = x^2}}}
{{{1600 = x^2}}}
{{{40 = x}}}