adult education
posted by Vanessa .
Math
If the line passing through the points (1,a) and (4,2)is parallel to the line passing through the points (2,8) and (7,a + 4), What is the value of a ? Please help, I don't understand how to set this one up.

If they are parallel, they have the same slope.
line slope=(a+2)/(3)
second line slope=(a+4)/(9)
set them equal and solve for a.