If you get stuck, one way to get un-stuck is to simply plug in #s and see what happens. After a few #s, you should get a feel for how the equation behaves.

n=0; V = 29,000

n=1000; V = 29,000 - 1000\*0.25 = 29,000 - 250 = 28,750

n=10,000; V = 29,000 - 2500 = 26,500

n=100,000; V = 29,000 - 25,000 = 4,000 \[I went too far <passed my desired value of 5,000; at least you know the answer is n < 100,000\]

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This isn't the mathematical way of solving something but it's a way to get you thinking along a different path.