There no difference between x-12=y and y=x-12
Answer:
The length of EF = x = 18 cm
Option A is correct.
Step-by-step explanation:
Ware given perimeter of triangle = 97 cm
We need to find length of EF = x = ?
The length of EG = x+7
The length of EF = x
The length of GF = 3x
The formula used is: 
Putting values and finding x i.e length of EF

So, value of x=18 cm
The length of EF = x = 18 cm
Option A is correct.
There are going to be two solutions because the "biggest" x is x^2 but you can factor to find what they actually are.