Step-by-step explanation:
first factorize the numbers
8=2^3
28= 2×2×7
now
9√2 - 3√7 + √2×2×2 -√2×2×7
as the square root is given you can take the squares out of the root
9√2 - 3√7 + 2√2 - 2√7
(9 +2 )√2 - (3+2)√7
11√2- 5√7
here's the answer
