If we place what the husband earns as h and what the wife earns as w, we can begin...
w + h = 110000
but w = 2h - 16000
We can turn it into..
2h - 16000 + h = 110000
Which we can then combine into..
3h - 16000 = 110000
Add 16000 and..
3h = 126000
Divide by three...
h = 42000
(nice)
The husband earns 42,000$ a year
Bonus: The wife then earns 68,000$
42,000 (or h) + 68,000 (or w) = 110,000
Because this is the original equation, we are correct.