First set everything to 0. Giving you A= 1 , B= 1 and C= -5 Then input everything into the quadratic formula and either solve by hand or use a calculator. Note exact values are found by hand, decimals are found using a calculator.
Each of the oranges would sell for 50 cents so 10*0.50=5 dollars And for the grapefruit each cost 80 cents so 11*0.80=8.80 So in total he would spend 13 dollars and 80 cents.
