Plugging -2 in for x you get | -2(-2) - 6| which is |4-6| since a negative times a negative is a positive and 2 time 2 is 4. Subtracting you get |-2| which is 2 since the absolute value of -2 is 2.
The answer is 2 because when you substitute (-2) for x in -2x you’ll get 4-6, then you subtract it to get (-2) and since there is an absolute bracket you change it to a positive, there for the answer is 2.