The first one is easy;

30*40 + ((20^2 * pi/2)-(10^2*pi/2)) = 1200 + 150pi = E

The second one;

the hypotenuse of the whole triangle is 5, so use the following equation where 5 is split up into x and 5-x, so,

sqrt(3^2-x^2) = sqrt(4^2 - (5-x)^2)

solve that equation and you get x = 9/5 or 1.8

Then, we use the Pythagoras theorem;

sqrt(3^2 - (9/5)^2) = sqrt(144/25) = 12/5

Eplanation reattached.