The line passes through points A (2, 1) and B (3, y) with slope 4.
Using the slope formula:
Slope=x2−x1y2−y1
Where A (2, 1) gives x1=2 and y1=1, and B (3, y) gives x2=3 and y2=y.
Substituting into the slope formula:
4=3−2y−1
4=1y−1
4=y−1
Solving for y:
y=4+1
y=5
Therefore, the value of y is 5.