make 2 equations one for the price and one for quantity. so first set x = AA and y= AAA. for price 37= 1x+.75y. now for the quantity we have x+y=42. Now we can solve by subtracting the equation for price from the equation for quantity and we get .25y =5. solving this we get y= 20. Now we plug that value back in and solve for x. 22 double A's and 20 triple A's.