X is 15 inches long.
Work is shown in the picture
-3x, and 7(x-4) are all terms.
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?
<h3>We learned how to write algebraic equations, and some further information on multiplying.</h3>
Answer:
B. Rational
Step-by-step explanation:
Any number which can be represented as a ratio in the form of a fraction is a rational number.