Answer:
The equation should look something like this.
Be careful with your use between cubing and multiplying; Cubing is multiplying the number by itself multiple times, while multiplying is like repeated adding, yet much easier.
In this case, if it says triple, I highly recommend multiplying by 3, which is what I did, it only looks different because it is in parentheses.
What have we learned?
We learned how to write algebraic equations, and some further information on multiplying.