I will take M as molly and S as her sister
M=x-5
S=x
M+S=37
X-5+x=37
2x-5=37
Now you add 5 on both sides so you get 2x=37+5
-5 on other becomes 0 because when you add +5 and -5 get cancels out
So I am left with 2x=37+5
2x=42
Than you divide 2 on both side to get x alone so you are left with
X=(42/2)
X=21
Molly’s age equation is x-5
Now you plug x into the equation so you get
21-5
And that’s equal to 16
So Molly’s age is 16 years
