You'll have to get this equation back to the y=mx+b form to find your y intercept. Start by getting y alone.
3x + 2y = 7
-3x -3x
2y = -3x + 7
Since why has a 2 in front of it, you now need to divide the entire equation by 2 to get y completely alone.
2y = -3x +7
/2
y= -3/2x + 7/2
Normally, you'd want to simplify the fractions but that is the smallest you can get it to be. Your y intercept is 7/2.