The slope is 1.5x
Per x value increase, the y value increases by 1.5.
This mean that if x is 2, the y value will be 3 higher than the y-intercept.
We can use the slope formula to verify this.

6 - 4.5 / 0 + 1
1.5/1 = 1.5
This line in slope-intercept form would look like this:
y = 1.5x + 6