The cost is c=.46 +.20(z-1)
Solve for z
To solve for z, first we remove the parenthesis
c= .46 + .20z - .20
combine like terms
c= 0.26 + 0.20z
Now we need to get z alone
Subtract 0.26 on both sides
c - 0.26 = 0.20z
Now divide both sides by 0.20
[tex]\frac{c-0.26}{0.20}=z[/tex]
We got z alone
[tex]z=\frac{c-0.26}{0.20}[/tex]