To find the whole answer, let's look at each multiplication:
[tex]\frac{5280ft}{1\text{ mile}}\cdot\frac{30\text{ miles}}{1\text{ hour}}=\frac{5280ft\cdot30\text{miles}}{miles\cdot hour}=\frac{158400ft}{\text{hour}}[/tex]Now, it changes from hours to minutes:
Use, 1hour = 60 minutes
[tex]\frac{158400\text{ ft}}{1\text{ hour}}\cdot\frac{1\text{ hour}}{60\text{ minutes}}=\frac{158400\text{ ft}\cdot\text{hour}}{\text{hour}\cdot\text{ 60 minutes }}=\frac{158400ft}{60\text{ minutes}}[/tex]Then, it changes from minutes to seconds:
Use, 1 minute = 60 seconds
[tex]\frac{158400\text{ ft}}{60\text{ minutes}}\cdot\frac{1\text{ minute}}{60\text{ seconds}}=\frac{158400\text{ ft}\cdot1\text{ minute}}{60minutes\cdot60\text{seconds}}=\frac{158400\text{ ft}}{3600\text{ seconds}}[/tex]Then:
[tex]\frac{158400\text{ ft}}{3600\text{ second}}=44\text{ f}eet\text{ per second}[/tex]