Pupils at a scholl either arrive by bus, car or on foot. 3/10 walk and 1/3 come by bus. What fraction come by car?

The total of the pupils are the 100%, or in fraction mode, 1, the whole, so we have:

bus + car + foot = total

1/3 + car + 3/10 = 1

car = 1 - 3/10 - 1/3

car = 1 - (9/30 + 10/30)

car = 30/30 - 19/30

car = 11/30

that is the fraction that come by car