Set up a proportion:
kid/dad = kid/dad
8/9 = 5.5/dad
Cross multiply to solve proportions:
8*dad = 9*5.5
8*dad = 49.5
dad = 6.1875 feet
They want inches so multiply by 12:
74.25 inches
They want "nearest inch" so:
Dad is 74 inches tall.
9.5m questions
12.2m answers