Final answer:
The system of equations that can be used to find the amount of Kentucky blue grass and Tall Fescue Mr. Alvarado purchased is x - y = 20 and 9x + y = 168.
Step-by-step explanation:
The system of equations that can be used to find the amount of Kentucky blue grass (x) and Tall Fescue (y) Mr. Alvarado purchased is:
a) x - y = 20;
9x + y = 168
In this system of equations, the first equation represents the total amount of grass seed purchased, which is 20 pounds. Since Mr. Alvarado bought grass seed from two types, Kentucky blue grass and Tall Fescue, the second equation represents the total cost of the grass seed, which is $168. By solving this system of equations, you can find the values of x and y, which represent the pounds of Kentucky blue grass and Tall Fescue purchased, respectively.