Let x = the number of the $24.99 cartridges sold. Then the number of the $15.99 cartridges is (47-x). The equation for total money received is 24.99x + 15.99*(47-x) = 940.53. From the equation, x == 21. ANSWER. 21 cartridge at $24.99 and the rest, 47-21 = 26 cartridges at $15.99.