if we select a birth at random, what is thew probability the mother is 19 years of age or younger?

2 answers

You haven't posted the data to determine this answer.
For Canada, see statistics for 2007

http://www.statcan.gc.ca/pub/84f0210x/2007000/t008-eng.htm

from which we can extract the following information:

live birth for all ages = 367,864
live birth for 15 & under = 119
live birth for 15-19 = 15161

(frequential) probability for birth by mother 19 and younger=(?+?)/(?)

Can you take it from here?