First figure out how many hours total Jake works by adding the time spent mowing the lawn to the time spent planting flowers: 1 hour + 2 hours = <<1+2=3>>3 hours
Then figure out how much money Jake makes if he earns $20/hour for three hours by multiplying the time spent by the pay rate: $20/hour * 3 hours = $<<20*3=60>>60
Then subtract the money Jake gets paid for mowing the lawn from the total to find how much he should charge in total for planting the flowers: $60 - $15 = $<<60-15=45>>45
#### 45