Think of a number. Double the number. Subtract 6 from the result and divide the answer by 2. The quo

Think of a number. Double the number. Subtract 6 from the result and divide the answer by 2. The quotient will be 20. What is the number

Let's call our number n.

Double the number means we multiply n by 2:
2n

Subtract 6 from the result means we subtract 6 from 2n:
2n - 6

Divide the answer by 2:
(2n - 6)/2

We can simplify this as n - 3

The quotient will be 20. This means the simplified term above is set equal to 20:
n - 3 = 20 <-- This is our algebraic expression

If you want to take it a step further, and solve for n in the algebraic expression above, we type this expression into our calculator, and get:
n = 23