There are 16 students in a class. Each student has either a bicycle or a tricycle. There

are exactly 37 wheels altogether. How many bicycles do the students have?

x = number of students that own a bicycle

16-x = number of students that own a tricycle

total wheels = number of bikes x 2 and number of tricycles x 3

you get 2 * x + 3 * (16-x) = 37

2x + 48-3x = 37

-x = - 11x = 11

11 students own bicycles and 5 own tricycles