Due while browsing in an antique store, cameron found this page that came from an old book of riddles

Let's first deal with the angles towards the top of the diagram. You should immediately notice that angle H is opposite the right angle and therefore angle H has a value of 90 degrees.
Now that will mean that the sum of the angles that are listed as (8m - 18) and (5p + 2) will add up to 90. And since the angle (7m + 3) is opposite to the (5p + 2) angle, they're equal. Therefore (8m - 18) + (7m +3) = 90. Let's see what m is
(8m - 18) + (7m +3) = 90
8m - 18 + 7m + 3 = 90
15m - 15 = 90
15m = 105
m = 7

Since m = 7, you immediately know that (8m - 18) = 38, and (7m + 3) = 52.
And because of the opposite angles, you also know that (5p + 2) = 52, so p = 10, and (11t - 17) = 38, so t = 5

The line CE has been divided into 2 equal halves by point D, so
5a + 12 = 9a - 12

Solving for a, gets
5a + 12 = 9a - 12
12 = 4a - 12
24 = 4a
6 = a

So a = 6

The two angles off of point E are marked as congruent, so
48 = 21s + 6
42 = 21s
2 = s

So s = 2.

Now let's arrange the variables in numeric order.
s = 2
t = 5
a = 6
m = 7
p = 10

And upon doing so I see the word "stamp" as the answer to the riddle "What sits in a corner but travels around the world?"