To get 10% of 40, you move the decimal point one way to the left. So 10% of 40 is 4 Now you need 2% and because you know 10% is 4, you divide that by 10 and multiply it by 2 because of the 2% 4/10=.4 .4•2=.8 Now you add them 4+.8=4.8 12% of 40 is 4.8