Hello!

Using the COUNTIF and COUNTIFS formula will allow you to count how many a

1) under30
2)30 to 40
3)40 to 50
4)50 to 60
5)older

So for under 30 and above 60, it's just a COUNTIF formula:
=Countif(Range, criteria)
Range is just column where the age is, then criteria is "<30", and "60"

For the middle ages, just do the COUNTIFS Formula:
=countifs(creteria_range1,Criteria1,Criteria_range 2,Criteria2...)
IN this case, Range is the same for all, but the criteria 1 is "30", then criteria 2 is "<40", so on and so forth.

Hope this helps!