Final answer:
To decrease a number by 18%, subtract 18% from 100% to get 82%, then convert this to a decimal, 0.82, and multiply the original number by 0.82.
Step-by-step explanation:
To decrease a number by 18%, we subtract 18% from 100% to find out what percentage we'll have left. So, 100% - 18% = 82%. Now, to convert this percentage to a decimal that we multiply the original number by, we move the decimal point two places to the left. The resulting decimal is 0.82. To decrease a number by 18%, you should therefore multiply it by 0.82.