Answer:
20 years old
Explanation:
Suppose the husband's age is h and the wife's age is w.
The average of two numbers is their sum divided by 2. So, the average age of the husband and wife is:
(h + w)/2 = 30
We know that h = 40, so plug this into the equation above:
(40 + w)/2 = 30
40 + w = 2 * 30 = 60
w = 60 - 40 = 20
Thus, the wife is 20 years old.
~ an aesthetics lover