Let the unknown value be x.
18 is 50% of ________n can also be written as;
18 = 50% of x
of means multiplication;
18 = 50% * x
18 = 50/100 * x
18 = 50x/100
cross multiply
18 * 100 = 50x
1800 = 50x
Divide both sides by 50
1800/50 = 50x/50
180/5 = x
x = 180/5
x = 36
Hence 18 is 50% of 36