Explanation:
we use the law of sine :
a/sin(A) = b/sin(B) = c/sin(C)
with the sides being opposite of the angles.
so, we have here now (sin(90) = 1)
b/sin(51) = c/sin(90) = 24/sin(39)
c = 24/sin(39) = 38.1363775... ≈ 38.1
b = 24×sin (51)/sin(38) = 29.63753176... ≈ 29.6