Question 1128288
Hi

g = m + 11
g+m = 59

We can treat these like simultaneous equations and substitute g for m + 11

m + 11 + m = 59
2m + 11 = 59
2m = 59 -11
2m = 48
m = 48/2
m=24

So Mikhail's age is 24 and Gabrielle's age is 35
35 + 24 = 59

In this sort of question you have to build two simultaneous equations. You don't have to substitute one equation in to another you could write

g = m+ 11
g + m = 59

And then

g - m = 11
g + m = 59

Because it is ± you add the two
so you get 2g = 70 so g = 35

35 -11 =24

Either way you get the right answer

Hope this was helpful