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(defn- calculate-freebies [purchased-chocolates wrappers-per-freebie]
  (loop [remaining-wrappers purchased-chocolates
         free-chocolates 0]
    (if (< remaining-wrappers wrappers-per-freebie)
      free-chocolates
      (let [new-chocolates (quot remaining-wrappers
                                 wrappers-per-freebie)]
        (recur
          (+ (rem remaining-wrappers
                  wrappers-per-freebie)
             new-chocolates)
          (+ free-chocolates new-chocolates))))))

(defn calculate-chocos [bobs-money cost-of-chocolate wrappers-per-freebie]
  (let [purchased-chocolates (quot bobs-money
                                   cost-of-chocolate)
        freebies (calculate-freebies purchased-chocolates
                                     wrappers-per-freebie)]
    (+ purchased-chocolates freebies)))

(defn calculate-freebies [purchased-chocolates wrappers-per-freebie]
  (loop [remaining-wrappers purchased-chocolates
         free-chocolates 0]
    (if (< remaining-wrappers wrappers-per-freebie)
      free-chocolates
      (let [new-chocolates (quot remaining-wrappers
                                 wrappers-per-freebie)]
        (recur
          (+ (rem remaining-wrappers
                  wrappers-per-freebie)
             new-chocolates)
          (+ free-chocolates new-chocolates))))))

(defn calculate-chocos [bobs-money cost-of-chocolate wrappers-per-freebie]
  (let [purchased-chocolates (quot bobs-money
                                   cost-of-chocolate)
        freebies (calculate-freebies purchased-chocolates
                                     wrappers-per-freebie)]
    (+ purchased-chocolates freebies)))

Note that I did go ahead and pull out calculate-freebies into a separate defn. I did that because a) it's a standalone concept and b) it makes calculate-chocos easier to read. If it weren't a standalone concept, I would have likely defined it in the let of calculate-chocos itself.

Update

Per OP's request, here is my solution:

(defn- calculate-freebies [purchased-chocolates wrappers-per-freebie]
  (loop [remaining-wrappers purchased-chocolates
         free-chocolates 0]
    (if (< remaining-wrappers wrappers-per-freebie)
      free-chocolates
      (let [new-chocolates (quot remaining-wrappers
                                 wrappers-per-freebie)]
        (recur
          (+ (rem remaining-wrappers
                  wrappers-per-freebie)
             new-chocolates)
          (+ free-chocolates new-chocolates))))))

(defn calculate-chocos [bobs-money cost-of-chocolate wrappers-per-freebie]
  (let [purchased-chocolates (quot bobs-money
                                   cost-of-chocolate)
        freebies (calculate-freebies purchased-chocolates
                                     wrappers-per-freebie)]
    (+ purchased-chocolates freebies)))

1. Yes, your tests are fine.
2. I found the code hard to follow without the requirements. To some degree, that's to be expected. Even once I read the requirements, there were things that I found hard to follow. More on that later.

1. Yes. Your tests are fine.
2. I found the code hard to follow without the requirements. To some degree, that's to be expected. Even once I read the requirements, there were things that I found hard to follow. More on that later.