Let x be your first alloy
2/5x+7/10(30-x)=1/2(30)
4x+210-7x=150
3x=60
x=20
So, you need 20 lbs of the first alloy, and 10 parts of the second to make 30 lbs of half iron and half silver alloy!
First do the the parenthesis: (6-3) = 3
Now you have [-4 + 3 * 8] -10
Next do multiplication: 3 *8 = 24
Now you have [-4 + 24]-10
Now do what is in brackets: -4 + 24 = 20
Now you have 20-10
Subtract 20-10 = 10
21x^2
you CAN'T factor 21x^2
