Question 741025
We are given:

The wheel shop sells other kinds of vehicles.There are bicycles and go-carts in a different room of the shop.Each bicycle has only one seat and two wheels and each go-cart has only one seat and only four wheels. There are a total of 21 seats and 54 wheels in that room. 

let x = number of bicycles, y = number of go-carts, then we have the following two equations:

x+y=21
2x+4y=54

solve second equation for x and we get
x=27-2y

substitute for x in equation 1 and we get

27-2y+y=21
-y=-6 and y=6 and x=15

so there are 15 bicycles and 6 go-carts