---------------------------------------------
Find Diameter :
---------------------------------------------
Circumference = πD
πD = 12π
D = 12
---------------------------------------------
Find Radius :
---------------------------------------------
Radius = Diameter ÷ 2
Radius = 12 ÷ 2
Radius = 6
---------------------------------------------
Find Area :
---------------------------------------------
Area = πr²
Area = π(6)²
Area = 36π or 113.10 units² (nearest hundredth)
---------------------------------------------
Answer: Area = 113.10 unit²
---------------------------------------------
12%=(3+10%*x)/(20+x)
x=30
add 30 pounds of the second alloy