The given function is
[tex]c=40p+75[/tex]Where 40 is the rate of change, and 75 is the y-intercept. This means that Joshua's earnings without the commission are $75, and he earns $40 per painting as commission.
Now, let's find the rate of change of the table
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]Let's replace the points (1, 115) and (2, 150).
[tex]m=\frac{150-115}{2-1}=\frac{35}{1}=35[/tex]So, the rate of change of the table is 35, which means the commission per painting is $35.
Now, we use the point-slope formula to find the equation
[tex]\begin{gathered} y-y_1=m(x-x_1) \\ y-115=35(x-1) \\ y=35x-35+115 \\ y=35x+80 \end{gathered}[/tex]As you can observe, the function shown in the table has 80 as the y-intercept, which means that the earnings without commission are $80.