Let A = Alvin, let E = Elga. We use these to set up a system of equations.
A + E = 81
E + 11 = A
We can rewrite that equation to be:
A + E = 81
- A + E = - 11
Now combine like terms:
2E = 70
E = 35
Plug back in to find A.
E + 11 = A
35 + 11 = A
46 = A
Alvin is 46 years old; Elga is 35 years old.
