how do you get the denominator for problem #1?

the 700 and 4.125???

ASTICITY he price of coffee rises from $3.00 to $5.25 while the quantity demanded falls from 800 cups to 600 cups. Ise the arc price elasticity of demand to compute the following: 1. Percent change in quantity. .-28.57% vantity - 600-800 -28.57% 700 -,52 54.547. $5.25 -03 4.125 2. Percent change in price. 54.547 - 3. Calculate the arc price elasticity of demand. = 52. (Inelastic) (lessthan I)