Question 688891
.10X+.90*600=.40(X+600)
.10X+540=.40X+240
.10X-.40X=240-540
-.30X=-300
X=-300/-.30
X=1000 OZ. OF 10% COPPER IS USED.
PROOF:
.10*1000+540=.40(1000+600)
100+540=.40*1600
640=640