What is the common difference of -10, -190, -390, -590

You have 3 boxes, one "strawberries"; one "mentos" and one "mixed".but you know that all the labels are in incorrect order .how do you know witch is witch?

Ihave trouble finding the nth term of a linear sequence

For the following geometric sequence, find the recursive formula. {-80, 20, -5, } i need : ')