#### Answer

The equation in slope-intercept form is $y=3$

#### Work Step by Step

Through $(-1,3)$ and $(0,3)$
The slope-intercept form of the equation of a line is $y=mx+b$, where $m$ is the slope of the line and $b$ is its $y$-intercept
Two points through which the line passes are given. Use them to find the slope of the line by substituting them into the formula $m=\dfrac{y_{2}-y_{1}}{x_{2}-x_{1}}$ and evaluating:
$m=\dfrac{3-3}{0-(-1)}=\dfrac{0}{1}=0$
The slope of the line and points through which it passes are now known. Substitute them into the point-slope formula of the equation of a line, which is $y-y_{1}=m(x-x_{1})$ and solve for $y$:
$y-3=(0)[x-(-1)]$
$y-3=0$
$y=3$