Answers:

a,

`2 \sqrt{1}/3+1/\sqrt{25-3^2}-(\sqrt{1/2})^2`

`=2/3+1/\sqrt{16}-1/2`

`=2/3+1/4-1/2`

`=5/12`

b,

`-\sqrt{25}. (-4)/\sqrt{225}- 5. \sqrt{121}/15+ (-3)^2`

`=-5. (-4)/15-5. 11/15+9`

`=4/3-11/3+9`

`=20/3`