The difference of twice a number and 9 is -21"

The number is -6

Step-by-step explanation:

We need to essentially "translate" this sentence into an equation. Let's break it down word by word.

"The difference of" means this is subtraction.

"Twice a number" means 2 multiplied by some unknown number. In math, unknown numbers are variables, so we can just call our variable "x". So twice a number means twice x, which is written as "2x"

"and 9". This means it would look like "2x-9"

"is -21" means "=-21" anytime you see the word "is" in these types of problems, it usually means that is the solution to the equation.

Now we have our equation, let's put it all together:

2x-9=-21

Now, solve for x accordingly, remembering PEMDAS:

2x-9=-21   First, isolate the variable. Get rid of the -9 by adding 9 to both sides

2x = -12    Continue to isolate the variable. Get rid of the 2 by dividing by 2

x = -6

the answer is a

step-by-step explanation:

because if you put 1 in to the square root of x it equals 300.

i think is 3 and 6. this took me 10 min to think.hope to and hope that my answer is brainliest.(follow me )