Subtraction fraction 1 3/10 - 7/15 HELP plz !! :)

ok here is how my question is worded exactly. At the start of my trip i have 1 3/10 litre of petrol. At the end i have used 7/15 of a litre of petrol. How much petrol do i have left ? if anyone could help plz help. And explain how you found the answer thanks :)

you have 1.3l of petrol at the start so,
initial level-petrol used=final amount of petrol
=13/10 - 7/15
=39/30-14/30
=25/30
=5/6
=0.83 liters

The petrol left at the end of your trip.
1 3/10-7/15 =13/10-7/15
=39/30-14/30 (lcd=30)
=25/30
=5/6 (reduce to lowest term)
Answer; 5/6 litre of petrol

13/10- 7/15

= [39- 14]/30

=25/30

=5/6

1 - 7/15 = 8/15

3/10 = 9/30

8/15 = 16/30

9/30 + 16/30 = 25/30 = 5/6 LITRE answer