The square pool is at the center of a square plot and this square plot is in their (maybe) yard. We know that this square plot has the sides that measure 34 m each and that the area of their lawn is 1056 m^2.
So, you find the area of the plot: 34 * 34 = 1156 and you subtract 1056 from it, so that you can find the area of the square pool.
1156-1056 = 100
To find the sides of the pool, inverse fornula of the area: square root of 100 = 10 m.
