The slope of the line can be calculated using the points (2,2) and (6,10):
Since the point (a,8) should belong to the same line, the slope should be the same using the points (a,8) and any other point. Since the slope is 2, use the points (a,8) and (2,2):
We got this expression for a:
Take the reciprocal of both sides of the equation:
Multiply both sides by 6:
Add 2 to both sides of the equation:
Therefore, a=5.