If you can multiply a number by 3 and then subtract 5,you will get 40.what is the number?

Let "a number" = x

3x - 5 = 40 is the equation you will use.

Note the equal sign, what you do to one side, you do to the other. Do the opposite of PEMDAS.

First, add 5 to both sides

3x - 5 (+5) = 40 (+5)

3x = 40 + 5

3x = 45

Next, to isolate the x, divide 3 from both sides

(3x)/3 = (45)/3

x = 45/3

x = 15

15 is your answer

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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:

answer: 1, 3 and 5 are correct

step-by-step explanation: