Answer:
The number is 6
Explanation:
"Think of a number," [I'm thinking of x]
"double the number" [OK, that would be 2x]
"and add 6 " [If you insist: 2x + 6] ["The Answer"]
"The answer is 3 times the number" [Answer = 3x]
We take the answer, 2x+6 and set it equal to 3x
2x+6 = 3x
x = 6