1. The problem states there are 120 cars in a multi-storey car park. 2. It also states that 30% of these cars are blue. 3. Calculate the number of blue cars: $$120 \times 0.30 = 36$$ blue cars. 4. To find the number of cars that are not blue, subtract the number of blue cars from the total number of cars: $$120 - 36 = 84$$ cars. 5. Therefore, the number of cars which are not blue is 84.