Ok, so in a case like this is important to remember that the square root of 377 is the number that equals 377 when it's multiplied by itself.
The best you can do with problems like this is calculate the square of the numbers you have on the line. In this case you have points between 0, 10, 20 and 30 and their squares are 0, 100, 400 and 900. 377 is between 100 and 400 so the square root of 377 must be between the square root of 100 and the square root of 400 which are 10 and 20.
the best choice for the location of the square root of 377 is between 10 and 20.