The first thing we must do for this case is find the factors of each of the numbers.
We have then:
60: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
90: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
Therefore the GCF is given by:
So, by rewriting the sum we have:
The error is not having written the GCF multiplying.
Answer:
Xiao did not write the sum as the product of GCF and the sum of two numbers.
The correct expression is: