Math
posted by Stephanie .
If the line passing through the points (a, 1) and (5, 7) is parallel to the line passing through the points (8, 8) and (a + 2, 1), what is the value of a?
a = ?

slope of 1st line is (71)/(5a) = 6/(5a)
slope of 2nd line is (18)/(a+28) = 7/(a6)
If the lines are parallel, the slopes are equal, so
6/(5a) = 7/(a6)
6(a6) = 7(5a)
6a36 = 7a35
a = 1
a = 1