Answer:
The variable "a number" stands for 9.
Explanation:
Rewrite the problem as 2 * (6 + x) = 30
Divide 30 into 2. 30/2 = 15
That means that the variable that is added to 6 must make the number 15.
15 - 6 = 9
The variable x is 9 so the equation would be:
2 * (6 + 9) = 30