Question

Roberto's Club has a secret knock for its Clubhouse door that only its members know. The members remember to knock on the door exactly n times in a row, were five more than three times n and is equal to the difference between 21 and n . How many times in a row do members knock on the clubhouse door?

Answer 1

`\text{ They knock 4 times on the clubhouse door.}`

Explanation:

Let n be the times that they knock on the door.

If five more than three times n and is equal to the difference between 21 and n;

`3n+5=21-n`

Solve for n, using inverse operations to solve equations:

`\begin{gathered} 3n+n=21-5 \\ 4n=16 \\ n=(16)/(4) \\ n=4\text{ } \\ \text{ They knock 4 times on the clubhouse door.} \end{gathered}`