Taryn mowed 9 lawns in 7.5 hers and received $112.50. Alastair mowed 7 lawns in 5 hrs, and received122.50. How much did Taryn charge to now the lawn, and how much did Alastair charge? If they both want to earn an additional $735 dollars each, how many additional hours will each spend mowing lawns? Explain.

If they both charged per hour worked and not per lawn mowed then we can calculate as follows.

Tarryn charged 112.50 for 7.5 hours.

So for each hour, Tarryn charged 112.5 / 7.5 = 15 dollars

For an additional 735 $ he will need to work 735 / 15 = 49

So Tarryn will need to put in an additional 49 hours of work.

Alastair charged 122.50 for 5 hours.

So for one hour, Alastair charged 122.50 / 5 = 24.50 dollars

To earn an additional 735 $ he will need to work 735 / 24.50 = 30

So Alastair will need to work for an extra 30 hours