Emily paid a total of $109.95 for 4 pairs of sandals and a pair of boots. each pair of sandals cost the same amount. the pair of boots cost $29.99. how much did 1 pair of sandals cost?

First of all, subtract the amount the boots costed from the total price. 
109.95-29.99 
= 79.96

Now you have the price of the 4 sandals. 
To find the price of 1 pair, divide this total by 4 

79.96 / 4
= 19.99 $ for one pair of sandals! 

A pair of sandals costs $19.99

Explanation:
First, let's first out how much 4 pairs of sandals would cost. Well, we know that 4 pairs of sandals and a pair of boots cost $109.95 altogether, and the boots itself cost $29.99, we want to subtract the boots out of the equation. So 109.95 - 29.99 = 79.96. Now we know that $76.96 represents the cost of 4 sandals. To find the cost of 1 sandal, we would divide 76.96 by 4, which is 19.99. Therefore, 1 pair of sandals costs $19.99