Please help with the last part of this maths question.

[Hera]

I can do the first 2 parts of this question (which I have included in case they add anything to part 3), but cannot work out the final part. Can any one put me out of my misery?

The number 65 bus goes on a circular route shown in the diagram below.
The cost of travelling between any two stops is worked out by adding
together the fares between consecutive stages. For example, if it costs 40p
to travel from A to B, and 37p to travel from B to C, then the cost of a ticket
from A to C would be77p.

If it costs 24p to go from C to D, and 97p to go from C to E, what is the fare
from D to E?

Mavis, Ethel and her friend Dot all get on the bus at E. Mavis buys a ticket
from E to G and is charged 82p. Ethel kindly buys a ticket for both herself
and her friend. Ethel is going all the way to G, whereas Dot is going to F,
Ethel is charged £1.17. What is the fare from F to G?

The total cost of one ticket from G to J and one ticket from G to I is £1
The total cost of one ticket from G to J and one ticket from H to J is £1.20
The total cost of one ticket from G to J, one ticket from G to H, and one ticket
from I to J, is £1.30.
What is the cost of one ticket from G to J?

A B C D E F G H I J [Bus stops arranged on a circle in the question)

[hermanmunster]

I can do the first 2 parts of this question (which I have included in case they add anything to part 3), but cannot work out the final part. Can any one put me out of my misery?
The total cost of one ticket from G to J and one ticket from G to I is £1
The total cost of one ticket from G to J and one ticket from H to J is £1.20
The total cost of one ticket from G to J, one ticket from G to H, and one ticket
from I to J, is £1.30.
What is the cost of one ticket from G to J?

A B C D E F G H I J [Bus stops arranged on a circle in the question)

I think if you make each little bit of the journey represented by a letter so GH=a HI=b IJ=c
so G to J = a+b+c

hence 2a+2b+c=£1
a+2b+2c=£1.20
2a+b+2c = £1.30

add the lot together : 5a+5b+5c = £3.50 so one trip a+b+c (or GtoJ)= 70p

[Hera]

I think if you make each little bit of the journey represented by a letter so GH=a HI=b IJ=c
so G to J = a+b+c

hence 2a+2b+c=£1
a+2b+2c=£1.20
2a+b+2c = £1.30

add the lot together : 5a+5b+5c = £3.50 so one trip a+b+c (or GtoJ)= 70p

Thank you. I have spent hours looking at that and now it is perfectly clear!