Start with "a ratio of 7 to 4:"
7 number of pepperoni pizzas 585
--- Equate this ratio to ----------------------------------------- = -------
4 number of plain pizzas p
Solve this equation of ratios for p, the number of plain pizzas sold.
Cross multiply: 7p = 4(585). Divide both sides by 7 to get the approx number of plain pizzas that are sold. Your final answer, the total number of pizzas sold, will then be 585 plus the value of p that you've just found.
