To find how long Andi and Kristy take to complete the job together, their work rates are combined using basic math.
To solve this problem, we can use the concept of work rates. Andi's work rate is 1 job per 2 hours, and Kristy's is 1 job per 4 hours. Combined, their work rate is 1 job per (1/2 + 1/4) hours. This simplifies to 1 job per 1/3 hours (or 3 hours).
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