Using the triangle we see that to find x we need to use the tangent function
tan 30 = x/42
x = 42tan 30
x = 24
to find the hypotenuse we use pythagorean thereom
24^2 + 42^2 = H^2
576 + 1764 = H^2
H^2 = 2340
H = |48|
length cannot be negative.
Therefore the sides are 42, 24, and 48