Answer: Tony's Fun Emporium.
Step-by-step explanation: If you have $21, you should go to Tony's Fun Emporium because the cost of riding 10 rides at Mark's Entertainment World is $30, which is more than your budget. At Tony's Fun Emporium, you can ride 6 rides ($5 entry fee + $1 * 6 rides = $11), which is within your budget.