What are the lengths of the legs of a right triangle in which one acute angle measures 19° and the hypotenuse is 15 units long?

So you have a right angle triangle. You need to use trig for this, as you have two values you can figure out a third.

You know that you have

90 deg. angle
19 deg. angle
Therefor you have 71 deg. angle

sin19 = x/15
15sin19 = x
x = 2.2

Now do Pythagoras c^2-b^2=a^2

a = 14.8

So the sides are 2.2 and 14.8 units long. (If these numbers are wrong tell me and I'll edit answer)