Simplify

√x^5
a. x^2√x
b. x^3
c. x^3√x
d. x^4

√20+√40
a.5√5
b.√10
c.6√5
d. cannot combine terms

√36x+√100x-√25x
a.6√3x
b.-5√5x
c.11√x
d.7x√x

solve for x
√2x-3=7
a. x=5
b. x=7
c. x=19
d. x=50

The first is a. you can rewrite it


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.


the fourth is d.
add 3 to both sides 
then square both sides 
then divide both sides by 2, x=50