Answer
You finish first
Work Step by Step
We are given two functions:
$$\begin{align*}
y_1&=1200-50x\\
y_2&=1400-50x.
\end{align*}$$
The $x$-intercept of any of these functions represents the number of minutes after which you are done typing words.
The person who will finish first is the one who has a smaller $x$-intercept.
Calculate the $x$-intercepts:
$$\begin{align*}
1200-50x&=0\Rightarrow x=\dfrac{1200}{50}=24\\
1400-50x&=0\Rightarrow x=\dfrac{1400}{50}=28.
\end{align*}$$
So the first person to finish typing is you.
Note: Since the slope is the same (they type with the same speed), we could decide who finishes typing first by comparing the $y$-intercepts!
