1 A parking lot, 12 cars and motorcycles * * * stopped, and one * * * had 34 wheels. Every car has four wheels and every motorcycle has two wheels. How many cars and motorcycles are there in the parking lot?

There are x vehicles, 4x+( 12-x) = 34, and x is 5 12-5 = 7 (vehicles). A: There are five cars and seven motorcycles.

2 Hope the sixth grade boys 120, and the number of girls is 5/4 of that of boys. How many students are there in the sixth grade?

120×(5/4+ 1)=270 people.

Three kinds of insects, spiders, dragonflies, cicadas *** 18, * * * have 20 pairs of wings and 1 16 legs. How many people are there? Spiders have no wings and eight legs; Dragonflies have two pairs of wings and six legs; Cicada 1 has two wings and six legs)