Clare asks andre to play the following number puzzle: pick a number add 2 multiply by 3 subtract 7 add your original number andre’s final result is 27. which number did he start with?

ANSWER

He started with


EXPLANATION

Let the number be



When Andre adds 2, the number becomes,



When he multiplies by 3, the number becomes,



When 7 is subtracted, he gets,



When he adds the original number, he gets,



We now equate all this to 27,



We expand brackets to get,



Group like terms,

Simplify,






Hence the original number is 7.