Three times the square root of a number is the same as 4 less than the number. find the number

The problem is asking you to find x in this equation: 3×√x = x-4   I guessed and checked for this problem with numbers that were perfect squares like 4,9,16 etc. The number you are looking for is x=16 The square root of 16 is 4. 4x3=12 and 16-4 is 12. 
Hope I helped!