I'm back so
80% of 12=9.6 grams=gold so
so she wants to add to the alloy to make the gold 92.5% gold so
I'm not sure how to do A or B but I think the answer to B is 2.4 grams
C. so the jewler has 2.4 grams of alloy
we must find out when 2.4=7.5%, what is 100%
so if 2.4=.075x then 24=0.75x then 32 grams=100 %
so 32-2.4=29.6 grams
29.6/32=0.925 or 92.5%
this is not the legit way to do it