Because the coefficient is negative, think about whether the predicted time goes up or down as weeks of training increase.

The coefficient of $x$ tells the change in predicted $y$ for each increase of 1 in $x$.

Type $y=80-1.5x$.

Notice the number multiplying $x$ is $-1.5$. That number tells how much $y$ changes when $x$ increases by 1.

Click the table icon for the expression and compare two rows where $x$ differs by 1 (for example, $x=4$ and $x=5$). The $y$-values differ by $-1.5$, showing the predicted time drops by 1.5 seconds per week.

In $\hat{y} = 80 - 1.5x$, the coefficient of $x$ is $-1.5$. This is the slope.

A slope of $-1.5$ means that for each increase of 1 week in training, the predicted time decreases by 1.5 seconds.

Therefore, the correct choice is For each additional week of training, the predicted 400-meter time decreases by 1.5 seconds.