Slope-Intercept form = Y = mx + b
First, find the slope = m = y2 - y1/x2 - x1
4 - 2/3 - 1
2/2 = 1
So, you have figured out that your slope is 1, so plug 1 into m of your equation :
y = 1x + b
B is the y-intercept, so, Use the two points (1,2) and take the y and plug it into the equation:
y = 1x + 2
Hope this helps!!