I don’t understand this at all

Answer:
B = 61.0
Step-by-step explanation:
Since this is a right angle, we can use trig functions
sin theta = opp side/ hypotenuse
sin B = 7/8
Take the inverse of each side
sin ^-1 ( sin B) = sin ^ -1 (7/8)
B =61.04497563
To the nearest tenth
B = 61.0