so you just need to add the both firsnumber which is 3 and 1 is equal to 4 and second is you add the both second number whick is 8 and 8 is equal to 16 now that you got all the numbers needed to complete the fraction just put the 4 in the top and pu the slach or / and put the 16 in the bottom
The 10$ is added on because it's a one time exchange and the 8 is multiplied by the x because for every hour you add 8$ to the price and y is the total price at the end depending on x.