Trinity's science instructor entered the 7th students in a STEM competition. There was an enrollment fee of $50 and an additional fee of $12 for each packet of 10 tests. The total cost was $170. How many tests were purchased? Which of the following equations best models the situation? Question 1 options:
A12x + 50 = 170
B 50x + 12 = 170
C 12x - 50 = 170
D 50x - 12 = 170