To find the equation of the time they spent we need to use the:
![y-y_1=m(x-x_1)](https://img.qammunity.org/2023/formulas/mathematics/high-school/csobd57zth7rh9k4hz9amldzpq2owf0z4j.png)
Where m is the slope and (x1,y1) is a point of the table.
We can find the slope with:
![m=(y_2-y_1)/(x_2-x_1)](https://img.qammunity.org/2023/formulas/mathematics/high-school/78uaqhwt0aws3qfwxigaftpihnmb1gzxtp.png)
Using the first two points on the table we have:
![\begin{gathered} m=(10-7.5)/(4-3) \\ =(2.5)/(1) \\ =2.5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/5o4fxvq0nmi0shthzz0vpwwj7pzxqku3wt.png)
Now plugging the values of the slope and the first point into the equation we have that:
![\begin{gathered} y-7.5=2.5(x-3) \\ y-7.5=2.5x-7.5 \\ y=2.5x \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/mf5ogrc9efczune0enq4k0o4kqjx6xsrdm.png)
Therefore the equation that represents the time they spent is:
![y=2.5x](https://img.qammunity.org/2023/formulas/mathematics/college/e5hpd0uzej6orrbr611d9dfzo2fv5wn2rg.png)
where x is the number of people they survey and y is the time it takes.