Final answer:
In the expression 30x, the variable 'x' represents the number of days Dawson practiced soccer. Each day accounts for 30 minutes of practice, so multiplying by 'x' gives the total practice time.
Step-by-step explanation:
The expression 30x is used to find the total number of minutes Dawson has practiced soccer. In this expression, the variable x represents the number of days Dawson practiced. Since Dawson practices for 30 minutes each day, you would multiply the number of practice days by 30 minutes to find the total practice time. Therefore, the correct answer is B) The number of days Dawson practiced.