Method one

Assuming that nine cars are all two-wheeled, there should be two wheels * 9 = 18 (one), which is 22- 18 = 4 (one) less than the actual situation. This is because if the tricycle is counted by two rounds, each car will be counted 3-2 = 1 (one) less and four cars will be missing. Comprehensive formula: (22-2 * 9)/(3-2) = 4 (vehicle) 9-4 = 5 (vehicle)

It can also be assumed that all 9 vehicles are tricycles, and there should be 3 * 9 = 27 wheels, which is 27-22 = 5 wheels more than the actual situation. This is because if two wheels are counted as three wheels, each car will count 3-2 = 1 (wheels) and 5/ 1. Comprehensive formula: (3 * 9-22)/(3-2) = 5 (vehicle) 9-5 = 4 (vehicle)

Method 2

Solve with equations, but I don't seem to have learned equations in the fourth grade.