Please help im very confused

Ineed with number 17 i don’t get it at alll

What is the explicit formula for this sequence? -7, -4, -1, 2, a.) an = 8 + (b - 1)3 b.) an = -7 + (n - 1)3 c.) an = 3 + (n -1) (-7) d.) an = -7 + (n - )

Jude is making cement for a driveway. the instructions show the amount of each ingredient to make 1 batch of cement. complete each statement to adjust the ingredients for each new situation if jude uses these instructions.