The smiths spent 18% of the monthly income on food. The income in May was $3500.00. How much did they spend on food

To calculate the percentage of a quantity you need to multiply the percentage times the quantity, keep in mind that a percentage is a ratio of a number over 100, so we have:

18% = 18 out of a 100 = 18/100

and we propose the multiplication:

(18%) ($3500) = (18/100) ($3500)

= 18*3500/100

= 630

therefore, 18% of $3500 is $630, so they spent $630 on food