Holly’s expression seems to be a mix of terms involving variables m and n, but she made a mistake by not combining like terms properly.
Let’s break down the terms:
- Terms with m: 11m, 10m, m
- Terms with n: 13n, 7n, 20n
- Terms with both variables mn: 6mn, 3mn, 9mn
Now let’s combine the like terms:
- m terms: 11m + 10m + 1m = 22m
- n terms: 13n + 7n + 20n = 40n
- mn terms: 6mn + 3mn + 9mn = 18mn
The final combined expression should be:
22m + 40n + 18mn
Thus, Holly’s error lies in not correctly combining these like terms to simplify her expression.