a chemist has two alloys one of which is 5% gold and 15% lead and the other of which is 25% gold and 30% lead how many grams of each of the two alloys should be used to make an alloy that contains 40g of gold and 93g of lead ?

Answer 1

.05A+.25B=40 where A and B are the two alloys.
.15A+.30B=93

multiply equation 1 by three, then subtract.
.15A+.75B=120
.15A+.30B=93
or .45B=27 solve for grams of B
then solve for grams of A

Answer 2

B=27/.45=60 grams
.05A+.25*60=40
.05A=25
A=500 grams