Question 251776
let x=the average of the failing students
24-20=4 failing students

(4x+20*80)/24=75
1/24 (4 x+1600) = 75
x/6+400/6=75
multiply both sides by 6
x+400=75*6
x+400=(25*3)*(3*2)
x+400=(25*2)*(3*3)
x+400=50*9
x+400=450
x=50