Y=3x+2 is the equation of a straight line graph. where does it cross the y-axis?

The line crosses the y-axis at point (0,2). You know this because the slope intercept form is y=mx+b. y is any point on the y-axis. m is the slope of the line. x is and point on the x-axis. Finally, b is the y-intercept or where the line crosses the y-axis. As a result, your equation has a 2 for b. So, your answer would be: the line crosses the y-axis at point (0,2). 2 being where the line crosses the y-axis.