How do you know when a number is being multiplied by a variable?

A coefficient is a number multiplied by a variable.

its being multiplied by a variable when it is being multiplied by a letter

Step-by-step explanation:

a variable is a symbol, usually a letter, that represents a number

Ex.

x in 5x (5 times x)

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation: