+738 there's 2 ways to solve this.
1. you can just experiment, and you can see that a=0, b=2, and c=7
2. we see that a+b+a+c=b+c
2a+b+c=b+c
2a=0
a=0
from there, you can find the other values :)
+781 a+b=2
a+c=7
b+c=9
Add all three equations together to get 2a+2b+2c=18. We divide this equation by 2 to get a+b+c=9.
