Answer:
E(9) pls mark brainleast
Step-by-step explanation:
If you add the left sides you get 2a+2b=2c then add the right sides which is 18. Now you have an equation 2a+2b+2c=18 then you can factor out the 2 that becomes 2(a+b+c)=18 then divide by two on both sides then get a+b+c=9.
