Let B = bike speed and C = car speed
Translate the English into math:
C = B + 31.2
(B + C)8.5 = 544
Substitute
(B + B + 31.2)8.5 = 544
Divide by 8.5
2B + 31.2 = 64
Subtract 31.2 from each side
2B = 32.8 => B = 16.4 and C = 47.6
You should take these answers and make sure they corectly solve the problem as stated.