If I guess this question correctly, it should be in the second grade of primary school. Different ways for three people to ride in three cars. Three people use the code names of A, B and C respectively. A and C are all in red, A and C are all in white, and A and C are all in blue. (1*3) A red, B white, A red, B blue, A white, B blue. A blue, b, c red, a blue, b, c white. (1*3*6) Party A, Party B and Party C sit in red, white, blue, red, blue, red, blue and red respectively. A blue b red c white, a blue b white c red. (1*6) The final result is 3+ 18+6=27.