Percentage comparison of exam scores

We have:

• $A = 0.9 B \implies B = \frac{A}{0.9}$
• $B = 1.25 C = \frac{5}{4} C \implies C = \frac{4}{5} B$
• $C = 0.8 D = \frac{4}{5} D \implies D = \frac{5}{4} C$

Given $A = 72$: $B = \frac{72}{0.9} = 80$ $C = \frac{4}{5} \times 80 = 64$ $D = \frac{5}{4} \times 64 = 80$