Answer:
[tex]\boxed{\boxed{\pink{\bf \leadsto It \ will \ take \ 5 hours \ to \ travel \ 300 \ miles. }}}[/tex]
According to Question , a plane travels 120 miles in 2 hours. So here we will use unitary method .
[tex]\bf\implies If \ it \ covers \ 120 \ miles \ in \ 2 \ hours \\\\\bf\implies Then \ one \ mile \ will \ be \ covered \ in \ \dfrac{120}{2} hrs \\\\\bf\implies Hence \ 300 \ miles \ will \ be \ covered \ in \ \dfrac{2}{120}\times 300 hrs = \red{5 \ hours } [/tex]
Here it was a case of direct proportion in which if two things are directly proportional to each other. If one thing thing increases then the value of second also increases. Here if the time increases then the distance also increases