Question 892127
Let x = the # of bags she initially sold.
==> Total sales was 52x initially.  The total sales after selling 4 more bags is 4*$72 = $288

==> {{{(52x + 288)/(x + 4) = 57}}}

==> 52x + 288 = 57(x + 4)
==> 52x + 288 = 57x + 228
==> 60 = 5x ==> x = 12, the number of bags initially sold.
Thus, x + 4 = 12 + 4 = 16 bags sold all in all.