To explain that the expression 20m−60n+20 can be written as 20(m−3n), John first factors 20m as 20 ⋅ m and 60n as 20 ⋅ 3n, and leaves 20 unchanged. Then, he factors 20 from each term of the expression 20m−60n+20 and puts the remaining factors together within a pair of brackets.

• Explain why John’s reasoning is incorrect.

• Factor 20m−60n+20

• Explain how you found the answer.