Question

75% of what number is 27?

Answer 1

you can set this up as a proportion 

is         %
--        ----
of        100

the "is" is 27. the percent is 75% which by default makes the of our x

Answer 2

$Percent means out of 100. \\ \frac{75}{100}*x=27 \\ \\ \frac{(25)3}{(25)4}*x=27 \\ \\ \frac{3}{4}*x=27 \\ \\ x= 27* \frac{4}{3} \\ \\ x=9*4 \\ \\ \boxed {x=36 }$