Let x be the number of "green" tickets. Then the number of "blue" tickets is (7420-x). The total money equation is, therefore, 13.50x + 9*(7420-x) = 79830 dollars. From the equation, express x and calculate x == 2900. ANSWER. 2900 "green" tickets and the rest, (7420-2900) = 4520 "blue" tickets. CHECK. 13.50*2900 + 9*4520 = 79830 dollars. ! Precisely correct !