Asapthe probability distribution histogram shows the age distribution of giraffes at a zoo. what is p(8< x≤20) enter your answer, as a decimal, in the box.

OK.
USUALLY when they give you this kind of graph (histogram),
each bar tells you the NUMBER of individuals that fall into
that particular range.

This graph is a little bit different ... it's easier.
On this graph, they're showing you the PROBABILITY that
an individual is in that particular range. 
(The y-axis is labeled 'P', and they told us it's a "probability distribution".)

The graph is telling us that if you close your eyes and pick one giraffe,
he has a 25% chance of being 4 years old or younger, a 10% chance of
being between 4 and 8, a 35% chance of being between 8 and 12, and
a 5% chance of being between 16 and 20.

This is just a fancy, slightly confusing way of saying that 25% of the
giraffes in that zoo are 4 or younger, 10% of them are between 4 and
8, 35% of them are between 8 and 12, and 5% of them are between
16 and 20.

Before we worry about answering the question, we can spot a few
interesting things about the giraffe population at that zoo:   

-- There are NONE that are between 12 and 16 years old. Weird.

-- The percentages only add up to 75%. So 25% of the giraffes
must be older than 20 !  They're just not included on the graph.

OK. So the question asks:  What's the probability that a giraffe
you pick is between 8 and 20 ?

-- He's got a 35% chance of being between 8 and 12, no chance
at all of being between 12 and 16, and a 5% chance of being
between 16 and 20.

Can you see that his chance of being between 8 and 20 is

(35% + 0% + 5%) = 40%  ?