Answer:
15 bicycle and 6 go-cart.
Explanation:
Given that,
There are a total of 21 seat and 54 wheels in the room.
Assume there are x number of bicycle.
Since, each bicycle has only one seat and each go-cart has only one seat.
Then, the number of go-cart is (21-x)
There are two wheels in a bicycle.
Total number of wheel in x number of bicycle is = (2.x)=2x
There are four wheels in a go-cart.
Total number of wheel in (21-x) number of go-cart =4(21-x)
According to the problem,
2x+4(21-x)=54
⇒2x+84-4x=54
⇒2x-4x=54-84
⇒ -2x= -30
\Rightarrow x=\frac{-30}{-2}
⇒x = 15
Hence, there are 15 bicycle and (21- 15)=6 go-cart