Final answer:
The equation to describe the situation is 45454545 - x = 21212121, where x represents the number of ice cream sandwiches sold.
Step-by-step explanation:
To write an equation to describe the situation, we need to understand the given information. The ice cream truck started the day with 45 ice cream sandwiches (45454545) and sold some (ssss) during a stop at a busy park. After the stop, it had 21 ice cream sandwiches (21212121) remaining. Let's represent the number of ice cream sandwiches sold as 'x'.
The equation will be: 45454545 - x = 21212121
To solve the equation and find the value of 'x', we can subtract 21212121 from both sides of the equation:
45454545 - 21212121 = 24242424
Therefore, the equation that describes the situation is: 45454545 - x = 21212121.