Sum up all columns and rows. 1 row and 1 column would be incorrect. When these meet, will be the incorrect value.
Summing the values in the year 8 column gives 150 (whilst it is 145 in the table) and summing the cars row gives 107 (whilst it is 102 in the table).
Where these meet is 33 on the table.
Hence, year 8s going by car (33) is an incorrect value.