Each banana cost 30p so the total price for bananas will be "number of bananas x 30". Here, bananas are called by the variable x so this number can be written as "30x" and will change depending on the number of bananas considered.If we do the same thing with the oranges, we will end up with "45y" as y is the name of variable counting the number of oranges.
The final expression wanted is the total price so it is found by adding the individual prices found before. The expression will then be "30x + 45y".