The sixth grade of primary school, the second volume of the new curriculum standard, the series of mathematical method guides, 96 pages of additional questions, the second question, how to buy a fish tank? According to the meaning of the question, quantity multiplied by unit price =630, (quantity -3) multiplied by (unit price+1)=630. (To multiply 630, there must be 5 units) 14 times 45=630, and 42 times 15=630. So the price is 14 yuan, and there are 45 fish tanks. The specific solution is: let the original price be X yuan 3X+(630/X-3)(X+ 1)=630, that is, (X+ 15)(X- 14)=0, so X =