the first is a. you can rewrite it
[tex] \sqrt{x^5} = \sqrt{x^2x^2x} = \sqrt{x^2}\sqrt{x^2}\sqrt{x} = xx\sqrt{x} = x^2\sqrt{x} [/tex]
the second is d. the only common factor between 20 and 40 that can be taken out is the 4 which becomes a 2, but inside the square roots there is still a 5 and 10, which cannot be combined
the third is c.
[tex]\sqrt{36x} + \sqrt{100x} - \sqrt{25x} \\ 6\sqrt{x}+10\sqrt{x}-5\sqrt{x} \\ 11\sqrt{x} [/tex]
the fourth is d.
add 3 to both sides [tex]\sqrt{2x} = 10[/tex]
then square both sides [tex]2x=100[/tex]
then divide both sides by 2, x=50
