Answer:
Assuming every single ball has an equal chance of being drawn, then if B is the probability of drawing a blue ball and R is the probability of drawing a red ball:
B + R = 1,
since either a red or blue ball will be drawn. Since each ball has an equal chance of being drawn:
16 p = 1, or
p = 1/16
where p is the chance to draw a single ball. Since there are 10 red balls, there are ten independent and different ways to draw a red ball, which means that
R = 10 p = 10/16 = 5/8.
You can either apply the first equation to find that
B = 1 - R = 3/8
or state directly that
B = 6 p = 6/16 = 3/8
since there are six independent and different ways to draw a blue ball from the bag.