How do you find the slope and y intercept for x + 2y=3?

Re-arrange your terms into the form $y = m x + b$ then $m$ will be the slope and $b$ will be the y-intercept
$x + 2 y = 3$
$2 y = - x + 3$
$y = - \frac{1}{2} x + \frac{3}{2}$
The slope is $- \frac{1}{2}$ and the y-intercept is $\frac{3}{2}$