She gets five dollars an hour so for one hour she gets five dollars, for two hours she gets 2 times 5 dollars (10 dollars), for three hours she gets 3 times 5 dollars (15 dollars) etc...
Now replace the 1,2,3... with the variable representing the hour. In this case it would be h. So 5h=five dollars per hour. Because you only put the kid to bed once, you add four at the end
