Answer:
Since Zohar is 6 1/2, Maria must be 16 1/2.
Explanation:
There are two equations, but they can be collapsed into one (and solved!):
M = Z + 10
M + Z = 23
(Z+10)+Z = 23 <<< this equation represents the stated problem, with one unknown
2Z = 13 <<< simplified
Z = 13/2 = 6 1/2 <<< solved (it is very unusual for age problems to have fractional answers)
