The square root of 53 lies between 7 and 8.
There are a couple ways to find this. You could...
A. Use a calculator and simply find the square root of 53 (7.280...) OR
B. You could square each number (1^2, 2^2, 3^2...) until you get the closest 2 numbers (one less than and one greater than) to 53 (7^2 = 49) and (8^2 = 64).
I hope this helps!