Answer:
15
Step-by-step explanation:
a+b=8 becomes a=8-b
b+c=10 becomes b=10-c
c+a=12 becomes c=12-a
Now subtract two of the equations that contain the same variable. I’ll pick two that contain an a: c+a =12 & a+b=8. Subtracting the latter from the former eliminates the “a”s, leaving c-b=4. Adding b to both sides to isolate c gives c=b+4. From above we can take b=10-c to substitute for b in c=b+4, giving us c=(10-c) + 4). Simplify the right side to c=14-c, add c to both sides, giving 2c=14, & then divide both sides by 2 to obtain c=7.
Replace the c in b=10-c with 7 to have b=10–7, so that b=3.
You can choose which a to solve for. I’ll select a+b=8, substituting 3 for b to have a+3=8, subtract 3 from both sides, gives us a=5.
Finally add 5+3+7 together to find that a+b+c=15.
