The question is asking...
x% of 90 is 50
In math
"of" means multiply
"is" means equals
x% of 90 is 50 means
x% x 90 = 50
90x = 50
x = 50/90
x = .5555
Multiply by 100 to convert to percent (move decimal 2 places to the right)
.5555 = 55.55% = 55.6% rounded to the nearest tenth