So sam can solve 30 multiplication problems in 2 min, how much questions can he solve in 20 min? do we have to divide 2 by 20 or do something else?

30 divide by 2 = 15 so thats how we know that sam can solve 15 questions in 1 minute. Now, in order to find how many can be solved in 20 minutes we simply multiply 15 and 20:

15 x 20 = 300.

Sam can solve 300 questions in 20 minutes.

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:

step-by-step explanation: