Calculating the slope of a line involves using a simple algebraic equation after identifying two points on the line. The equation is as follows: slope = (y1 - y2) / (x1 - x2).

**Identify two points on the line**To identify two points on a line, assign them coordinates on horizontal and vertical planes, making the vertical plane y and the horizontal plane x. Your two points are then identified as (x1, y1) and (x2, y2), or for example, (2, 1) and (6, 4).

**Use the slope equation**Use the slope equation to figure out the slope of a line. In the case above, the equation would read as follows: slope = (1 - 4) / (2 - 6) = -3 / -4 = 3/4.

**Reverse the choice of numbers**Note that it doesn't matter which point you choose as the first one, (x1, y1), and which point you choose as the second one, (x2, y2), for the slope equation to work. This can be seen by using the example above, choosing (6, 4) and (2, 1) as the two points. The slope equation would then be applied as follows: slope = (4 -1) / (6 - 2) = 3/4. The slope of the line remains the same.