Answer
$z$ - $\frac{1}{2}$ $=$ $z$ $\times$ $\frac{1}{2}$
Work Step by Step
The "difference" means subtraction; using the values in the order they are given in the problem. The difference of $z$ and one-half.
$z$ - $\frac{1}{2}$
"is" translates into an equals sign: $=$
The "product" means to multiply the values given.
$z$ $\times$ $\frac{1}{2}$
OR
$z$ - $\frac{1}{2}$ $=$ $z$ $\times$ $\frac{1}{2}$
