Question

Math geometry placemats

Answer 1

Let's call the missing side ? as shown in the problem.

Now set up a equation where everything adds up to 28x+11

?+8x+2+8x+2+5x+12=28x+11

?+21x+16=28x+11

?=28x-21x+11-16

?=7x-5

So 7x-5 is the missing side!

Hope it helps :D