There are a total of 68 cars in the parking lot (sum of all values on the table).
Selecting blue OR a chevy, means all blue and all chevies are valid choices...there are 7+9+8+7+5 (blue cars and chevy cars) = 36:
36/68 = 9/17
Selecting blue AND a chevy - There are 8 blue chevies:
8/68= 2/17
GIVEN that the car is blue means we're only selecting from the 7+9+8 = 24 blue cars on the lot which are chevies...and there are 8 blue chevies:
8/24 = 1/3