If I think of a number, I multiply it by 3, then I add 30, the result I have divided by 11, the result is 1 and in the end I divide it by 7 I get the number 2. What number was he thinking?
The easiest way to find the solution is to undo all the operations that have been carried out.
We know that the final result is 2 and the last operation has been divided by 7, so the previous result is 14. The previous operation is subtract 1, so the previous result is 15. As this number comes from dividing by 11, the previous result will be 11 * 15 = 165. Now, the previous operation is to add 30, so the previous result will be 135. And the first operation has been multiply by 3, so that the starting number would be 135 / 3 = 45.