The cube of a number means to self-multiply a number three times.
For example;
5 cubed, or 5^3 (using exponential powers).
This means to multiply 5 three times.
5 • 5 • 5.
Let's break it down.
5 • 5 = 25
25 • 5 = 125.
5^3 (or 5 cubed) is 125.
Now that we've explained what we're dealing with, let's proceed to answer the question.
The question asks, "What is the cube of 6?"
Remember what it means to cube a number.
Multiply 6 three times.
6 • 6 • 6
Break it down.
6 • 6 = 36
36 • 6 = 216.
The cube of 6 is 216.
I hope this helps!