Question 251677

let n= tests already taken
a=previous average
(97+n*a)/(n+1)=90
(73+n*a)/(n+1)=87
b)7
previous average was 89
check
(97+(7*89))/8=90
(97+623)/8
720/8=90
90=90
(73+(7*89))/8=87
(73+623)/8=87
696/8=87
87=87