Maths - Talk moves in our team discussions

For our maths class, we have been working on doing talk moves for the last few weeks. I had Quasia, Ashley, and Rowana in my group and our group name was "Royals". The question that were asked was? The petrol prices went up overnight and now one litre of gas at most petrol stations are $2.18. 


My car needs 20L to be on full so how much do I have to pay? and The petrol price remains at $2.18 but I need to fill my truck for a trip down to Hamilton. My truck needs 60L to be on full so how much will I pay? So we worked it out on our pieces of paper to see if we can use different equations in our minds, not using cheat or calculator.