Answer:
In December,
Joe collected: 231 bottle caps
Bill collected: 204 bottle caps
Explanation:
Joe averaged 320, so 320 x 12 = 3840
Bill averaged 340, so 340 x 12 = 4080
Joe and Bill had collected total 11 months, December should be collected:
Joe = 3840 - (300 + 412 + 207 + 283 + 601 + 114 + 319 + 299 + 403 + 317 + 354)
Joe = 3840 - 3609
Joe = 231
Bill = 4080 - (413 + 286 + 395 + 250 + 174 + 228 + 370 + 419 + 450 + 684 + 207)
Bill = 4080 - 3876
Bill = 204