Official Solution:In October, Jack earned 25% more than in September; while in November, he earned 20% less than in October. If Jack earned $200 more in October than in September, what was his combined income for the autumn?A. $1200
B. $1800
C. $2000
D. $2400
E. $2600
Let \(S\), \(O\), and \(N\) represent Jack's incomes in September, October, and November, respectively.
From the given, \(O = 1.25S\) and \(N = 0.8O\). Therefore, \(N = 0.8 *1.25S = S\). Given that \(O - S = 0.25S = \)200, we can deduce that \(S = \)800. Using this, \(O = 1.25*800 = \)1000 and \(N = S = \)800.
The total income for the autumn, \(S + O + N\), amounts to \(800 + 1000 + 800 = \)2600.
Answer: E