Answer:
Step-by-step explanation:
Alright, lets get started.
The given expression is : 
In very first step, Lisa made a mistake.
Lisa took 3 as common factor out and what she wrote is 3 (1+x) but when she took 3 as common factor, the expression would be 3 (x+2x)
Here she made a mistake.




So, the correct answer is 7x+3 : Answer
Hope it willhelp :)