a. f(a) =5a+12
we have 1. a=6
Therefore, where ever we find a we'll substitute in 6
f(6) =5(6) +12
6f=30+12
6f=42
so therefore 1. a=6 will match c on the right
2. a=2
f(2) =5(2) +12
2f = 10+12
2f = 22
therefore 2. a=2 will match a on the right
3. a=4
f(4) =5(4) +12
4f=20+12
4f=32
therefore 3. a=4 will match d on the right
4. a=5
f(5) =5(5) +12
5f=25+12
5f=37
therefore 4. a=5 will match b on the right
