I think a number. If a substract 8 from it and multiply by 3, the result is 21?

Answer 1

Let's start by setting up an equation to represent the given information. Let the unknown number be represented by 'x'.
According to the information provided, "If I subtract 8 from it (the number) and multiply by 3, the result is 21." Mathematically, this can be expressed as:
3(x - 8) = 21.

Now, let's solve this equation to find the value of 'x':
3(x - 8) = 21
Divide both sides of the equation by 3:
(x - 8) = 7
Add 8 to both sides of the equation to isolate 'x':
x = 7 + 8
x = 15.

Therefore, the number you were thinking of is 15.