Let's convert the height to inches...
5 × 12 = 60 + 4 = 64 inches
Now we find the actual height by setting it to x and solving...
90% of x = 64
.90 × x = 64
x = 64/.90
x = 71.11 inches
Lets round down to 71 inches. Now we convert back to feet and inches
71 ÷ 12 = 5 with remainder of 11 so 100% of her height is...
5 feet 11 inches
