Final answer:
Equation 1 represents the sum of x and y equal to 20. Equation 2 represents 2.50 times x plus y equal to 15. Equation 3 represents the sum of x and 4 times y equal to 28.
Step-by-step explanation:
Equation 1: x + y = 20 represents a linear equation where the sum of x and y is equal to 20.
Equation 2: 2.50x + y = 15 represents a linear equation where 2.50 times x plus y is equal to 15.
Equation 3: x + 4y = 28 represents a linear equation where the sum of x and 4 times y is equal to 28.