Answer :
so the question wants you to add all the coins together then subtract 15% SO
16+28+32+4=80
so 15% of 10=10%+5%
5%=1/2 of 10% so
10% of 80=8
5% of 80=10%/2=8/2=4
8+4=12
he sold 12 coins
16+28+32+4=80
so 15% of 10=10%+5%
5%=1/2 of 10% so
10% of 80=8
5% of 80=10%/2=8/2=4
8+4=12
he sold 12 coins