Hey Savion24,
A monomial can be defined as a number (1,2,3,4), a variable (x,y,z), or the product of numbers and variables (4x).
A binomial is a polynomial with two terms.
A trinomial is a polynomial with three terms.
Now lets have a look at the expression 7x³.
The given expression is a monomial as it is the product of a number and variable.
→ Hope this helps,
AnthraX