Answer: D) 
Step-by-step explanation:
Let 'm' represents the number of Mylar balloons and 'l' represents the number of latex balloons.
Given : Mylar balloons cost $1.25 each l, and latex balloons cost $0.75 each.
i.e. cost of m Mylar balloons in dollars = 1.25 m
i.e. cost of l Latex balloons in dollars = 0.75 l
Then, the equations can be used to find the number of each type of balloon in a bunch of 18 balloons that costs $19 will be :-

Hence, the correct answer is Option D.