Answer: There are 12 more white and blue cars than silver and red cars.
Step-by-step explanation:
Since we have given that
During 20 minutes of watching, Ed noticed:
Number of black cars = 23
Number of red cars = 9
Number of blue cars = 17
Number of white cars = 25
Number of silver cars = 21
We need to find the number of white and blue cars are more than silver and red cars.
Total number of white and blue cars = 25+17=42
Total number of silver and red cars = 21+9 = 30
So, difference between them is 42-30 = 12
Thus, there are 12 more white and blue cars than silver and red cars.