Question

A batsman has a certain average of runs for 16 innings.in the 17th inning he scores 85 runs,thereby increases his average by 3 runs.what was the his average before 17th inning?

Answer 1

let a = his average after the 17th inning
then
(a-3) = his average before the 17th
a = 
multiply both sides by 17
17a = 16(a-3) + 85
17a = 16a - 48 + 85
17a - 16a = 37
a = 37 his average after 17 innings