The pattern requires multiplying each term by 3 and then alternately subtracting 3 and adding 3. We multiply 7 by 3 and subtract 3 to get 24, multiply 24 by 3 and add 3 to get 75, and multiply 75 by 3 and subtract 3 to get 228. Following the same rule, we multiply 687 by 3 and add 3 to get 2064. Therefore, the missing term is 2064.