Gavin was disappointed when his favorite basketball player only scored 20 points in last night's game. Gavin had expected him to score 50% more than that. How many points did Gavin expect his favorite player to score?

To find out how many points Gavin expected his favorite player to score, we first need to determine what 50% more than 20 points is.

1. Calculate 50% of 20 points: \[ 50% \text{ of } 20 = 0.5 \times 20 = 10 \]

2. Add this amount to the original 20 points to find the expected score: \[ 20 + 10 = 30 \]

Therefore, Gavin expected his favorite player to score \( \boxed{30} \) points.