What is forty percent of three-fourths?

3/4 = 75% 

10% of 75 = 7.5

7.5 * 4 = 30  = 30/100  = 15/50  = 3/10

In math the word "is" means equals and the word "of" means to multiply so i would replace those words to look like this... What = 40% x 3/4

so we need to multiply 40% and 3/4... some calculators can perform this but if not i would change both to decimals which would be (.4)(.75) and that equals .3 or 3/10