To solve this, you would set it up like so:
is/of = X/100 , X being the percentage you are trying to find.
then you would substitute what you know:
4/25 = X/100
then cross multiply to get rid of the fraction:
4 x 100 = 400
25 x X = 25X
then set it equal:
400 = 25X
then divide both sides by 25
25X/25 = X
400/25 = 16
then you have X = 16
