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
1520+10x=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