Answer: 11.) -6. 12.) 4/5
For the square roots, there should be a plus&minus sign but my keyboard doesn't have that.
13.) 3 14.) 8
explanation: For a square root, you are looking for a number that was multiplied by itself to become the number under the radical.
11 is a bit tricky since there is a negative sign before the radical. 6×6=36 -6 × -6 = 36. It seems they want only the -6 here.
4/5 ×4/5 = 16/25
For cube root, you need the number that is multiplied by itself three times. 3×3×3 = 27 8×8×8=512