Lets call the roller coaster "y"
and the Farris wheel "x"
Nan rode y 8 times
8y
You know that 8y is going to be twice as many as the x
8y=2x
You should always try to get the y by itself on one side of the equation. You can do this by dividing everything by 8
y=1/4x
Now your equation is compleate