Don't post multi-megabyte images when you only need a few kB -- few of us are going to download such large files.
Without downloading your file, the obvious question to ask yourself is whether the 2kΩ resistor is part of the circuit you are trying to find the equivalent of. Remember that the idea is to replace part of the circuit with a black box that is equivalent to it -- with that resistor be part of the circuit that gets replaced or not? You analyze the part that is going to be replaced, nothing more and nothing less.
Given just that, then you are being asked to find a Thevenin Equivalent that is equivalent to the entire circuit as seen between nodes 'a' and 'b', so that includes the 2kΩ resistor. It will usually be pretty obvious when you should include something, often because it is a load element or a non-linear element. Any time that you are trying to find out something about a particular component, such as the current through it, the voltage across it, or the power associated with it, that component has to be kept out of the equivalent circuit because the equivalent circuit is ONLY equivalent in terms of the voltage/current characteristic at the terminals.