Find $m$ using $m=\frac{y_2-y_1}{x_2-x_1}$.

After you know $m$, plug one labeled point into $y=mx+b$ and solve for $b$.

In Desmos, enter the points $(2,18)$ and $(8,42)$.

Use the Line tool (or enter y-18= m(x-2) after computing $m$) to represent the line through the two points.

Find the slope $m$ between the two points and then compute $b$ using $b=y-mx$ for one point. This gives the equation $y=4x+10$.

Use the two labeled points $(2,18)$ and $(8,42)$:

Substitute $(2,18)$ into $y=4x+b$:

So $18=8+b$, which means $b=10$.

With slope $4$ and intercept $10$, the line of best fit is $y=4x+10$.

Therefore, the correct choice is $y=4x+10$.