How much of an alloy that is 40% copper should be mixed with 300 ounces of an alloy that is 80% copper in order to get an alloy that is 50%?

X=40% amount
300-x=other amount

0.4x+300(0.8)=(x+300)0.5
expand
0.4x+240=0.5x+150
minus 0.4x both sides
240=0.1x+150
minus 150 both sides
90=0.1x
times 10 both sides
900=x

add 900oz of the 40% alloy

There was 504 pages in that chunk