test preparation 💆🏻‍♀️💆🏻‍♀️

Question

there are 9 bottles in devins refrigerator. he adds 3 full boxes of water bottles to the refrigerator, then he adds 2 more boxes that each has 1 fewer bottle than a full box, when he’s done there’s 67 bottles in the refrigerator

Answer 1

9 + 3b + 2(b - 1) = 67

Solve for b.