An alloy of tin is 15% tin and weighs 20 pounds. How many pounds of tin are in the alloy?

Percentage of alloy 1=15%

quantity of alloy 1 = 20 pounds

percentage of alloy 2=10%

quantity of alloy 2 = x pounds

total alloy = 12

quantity of total alloy = (20+x) pounds

15*20+10*x=12 (20+x)

300+10x = 240+12x

10x-12x=240-300

-2x = - 60

/-2

x=30

So the quantity of tin will be 30 pounds for 10% tin