Question

Gabrielle is 9 years younger than Mikhail. The sum of their ages is 81 . What is Mikhail's age?

Answer 1

Let g = gabrielle's age
Let m = Mikhail's age.

You can make two equations and then solve them using substitution:
Gabrielle is 9 years younger than Mikhail, so:
g = m - 9
The sum of their ages is 81, so:
m + g = 81

Substitute the first equation into the second equation:
m + (m - 9) = 81
m + m - 9 = 81
2m - 9 = 81
2m = 90

Can you solve for m?