Question 47908
According to the question as the average of the 4 test should be greater then 70, so on applying the formula of average and assuming that in 4th test he scored x, we get

=> (x + 90 + 76 + 66)/4 > 70

=> (x + 90 + 76 + 66) > 70*4

=> (x + 232) > 280

=>  x > 280 - 232

=> x > 48