Evaluate square roots asap

1. evaluate √x+20 when x=16. (answer in simplified radical form.)
a) 36
b) 24
c) 6
d) 4

2. evaluate √21 - x when x =9. (answer in simplified radical form.)
a) √3
b) 2√3
c) 3
d) 4

3. evaluate √21 - x when x =9. (answer as decimal)
a) 1.73
b) 3.46
c) 3
d) 4