# How do you write an algebraic expression for the phrase "a number minus the cube of 4"?

If $n$ is "a number", then it's $n - {4}^{3}$.
No real explanation here, just the fact that referring, arbitrarily, to "a number" signals the usage of a variable, that is represented by a letter. "minus the cube of four" can be interpreted as either $- {4}^{3}$ or $- 64$, although since we need our algebraic interpretation to be as close as possible to the description, it's more accurate to write $- {4}^{3}$.