Section: Mathematics Usage

25)
(YB is parallel to ZD)

If BAC = (a + 30) degrees, then ACD expressed in terms of a is:

1. a + 30
2. a + 150
3. 150 - a
4. 60 + a
5. a - 60

BAC and ACD are supplementary angles. Therefore they should total 180 degrees. Because we don't know the value of a, we can solve this by using

m ACD = 180 - (a + 30)
m ACD = 180 -a - 30
m ACD = 150 - a.