We will solve the problem:

"Line AB contains points A (1, 2) and B (2, 6). The slope of line AB is"

The slope m of the line through the points (x1, y1) and (x2, y2) is given by:

m = (y2 - y1)/(x2 - x1)

In our case (x1, y1) = (1, 2) and (x2, y2) = (2, 6). We plug the values in the slope formula and get:

m = (6 - 2)/(2 - 1)

m = 4/1

m = 4

The slope of line AB is 4.