Answer:
A) 20m
Explanation:
52^2 - 48^2 = b^2
√2704 - √ 2304 = √400
b^2 = √400 = 20
As this is Pythagoras as we do not have any 2nd angle measure.
if it was trigonometry we could use 90 degree as part of the sum
48/ sin(?)x90 = 52
Then try other angle by deducting angle shown from 90
m/sin (?) x 90 = 52 etc.
But to guarantee you would find the base you could use tan.