At what position on the number line is the red dot located?

Answer:
[tex]\sqrt21[/tex]
Step-by-step explanation:
[tex]\sqrt21[/tex] = 4.583
[tex]\sqrt15[/tex] = 3.873
[tex]\sqrt13[/tex] = 3.606
[tex]\sqrt27[/tex] = 5.196
Looks like it's closest to [tex]\sqrt21[/tex]