Answer:
a. 53
Explanation:
The side with length 15 is opposite the right angle, so it is the hypotenuse of the right triangle.
For angle x, the side measuring 12 is the opposite leg.
Our 3 items of interest are: angle, opposite leg, hypotenuse.
The trig ratio that relates the opposite leg to the hypotenuse is the sine ratio.
sin x = opp/hyp
sin x = 12/15
sin x = 0.8
Now we take the inverse sine of 0.8 to find the measure of the angle.
x = sin^(-1) 0.8 = 53 deg