If Musa scored 75 in biology instead of 57, his average mark in four subjects would have been 60. What was his total mark?

If Musa scored 75 in biology instead of 57, his average mark in four subjects would have been 60. What was his total mark?

Answer Details

Let x represent Musa's total mark when he scores 57 in biology and Let Y represent Musa's total mark when he now scored 75 in biology, if he scored 75 in biology his new total mark will be $\frac{Y}{4}$ = 60, y = 4 x 60 = 240
To get his total mark when he scored 57, subtract 57 from 75 to give 18, then subtract this 18 from the new total mark(ie. 240)
= 240 - 18
= 222