You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

Michelle began her pizza delivery route with 0.5 tank of gas in her car . When she made it back to the pizzeria , 0.16666666666666666 tank of gas was . How much gas did Michelle use ?
0.3333333333333333

Megan 's class is going on a field trip to the zoo . If each van can hold 5 people and there are 25 students and 5 adults going , how many vans will they need ?
6

In fourth grade there were 10 students at the start of the year . During the year 4 students left and 42 new students came to school . How many students were in fourth grade at the end ?

48