Chapter 3 - Solving Inequalities - 3-2 Solving Inequalities Using Addition or Subtraction - Apply What You've Learned - Page 177: a

$x\ge310-40$, where $x$ is the number of boxes to be bought

Let $x$ be the number of boxes needed to be bought for the next game. With $40$ remaining empty boxes and with the boosters capable of selling at most $310$ boxes each game, then $$ x\ge310-40 .$$