I understand everything you did and that was pretty easy.
I just wish I'll be able to do that on the test.....
When you first see that, what exactly is your plan? Do you just start writing everything out in terms of numbers and variables, simplify and hope something fits? (especially the last part of simplying to get 2m = 5 +3J , and then changing the second part of the question into 2m and 4*3/4 J and getting 3J, then you reveal the 5) It seems like that's what you did, which is oversimplifying the method but it worked here.
Before the test starts there is only one thought in my mind - one can answer every question they ask using the data they give. The question is - how much time do you take?
My plan is to never use variables and never write anything(I solved this question without writing anything though I admit I was doing nothing more than making these equations in my mind). The trouble is that the plan doesn't work sometimes. I read the question and I wanted to pick variables because 2 hrs, 3 times, 80% etc were too complicated to handle without variables though it was obvious that they will all fit in neatly (notice 5 hrs at 80% - we know 80% is 4/5 so we are left with 4 etc)
As for simplifying the equation, it is but a natural step. If you see 2x + 4y = 8, you simplify it to x + 2y = 4 whether you see an immediate need or not. In the next part, when I saw the 2M, it was obvious that a 3J was on the way. Had there been a 6M, I would have expected to see a 9J. Remember, in GMAT things always fit in together.
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