Question 4.3.3

\[x + z = 100\] \[z = 100 - x\] \[y = x z\]

\[y = x(100 - x)\] \[x = 100x - x^2\]

## 100 - 2 * x

\[y' = 100 - 2x\] \[x = 50\] \[y = 50\]