batsman makes a score of 87 runs in the 17th match and thus increases his average by 3. Find his average before 17th match

33 before 39 after / let the average before 17th match be a now after playing 17th match the overall average increases to 3 therefore 87 runs =16*3 + (a+3)

let the average of the first 16 matches be x/16, where x is the total number of runs obtained in these 16 matches.
since the average increases by 3 after the 17th match, we can write: (x+87)/17 = (x/16)+3
on solving for x, we get x = 576.
therefore, the average before the 17th match will be 576/16 i.e 36

36

36 ?