a good one ;)

Let the square footage of the garden be 360 sq.ft

If Larry can hoe it in 90 minutes then his rate is 360/90=4sq ft/minute
So in 30 minutes he would have finished 4*30=120 sq ft.

If Jim can hoe it in 60 minutes then his rate is 360/60 = 6sq ft/minute
So in 30 minutes he would have finished 30*6 = 180 sq ft

So in 30 minutes both Larry and Jim would have completed 120+180=300 sq ft that leaves 60 sq ft still remaining to be completed by Larry alone.

Now, if Larry works at the rate of 4sq ft/minute then for 60 sq ft he would take 60/4= 15 minutes Hence A

Experts .. Whats the answer 45 or 15?

knight247 is right in his solution, but they ask the total time Larry works,

so just add the 15mins to the half an hour already worked already. SO 45 mins