Answer:
The format of this equation is wrong
I would maybe say a Rhombus. They have two likes of symmetry ^^ Hope this helps!
Let x represent the amount to be added. The total amount of tin will be
15%·20 + 10%·x = 12%·(20+x)
(15%-12%)·20 = (12%-10%)·x
3%·20/2% = x
30 = x
30 pounds of 10% tin must be added to get a 12% mixture.
