This is what I got for it if it helps
So basically your doing unit rates? Well guess what, I'm studying about that also, and I have a little understanding about unit rates, have you done ratios before?
Answer: a = 1/6
Explanation: Convert the mixed number into an improper fractions. Which is 21/4.
Then you can do the butterfly method.
-2/2 and -2/-4 hoppeee it helps