
Answer:
a) Total number of Sandwiches and drinks purchased  =  x + y
b)The three possible solution to the given equation  is
: (25,4), (20,8) and  (15,12)
Step-by-step explanation:
Number of sandwiches in Lunch  = x
Cost of each sandwich  = $4
Number of Drinks in Lunch = y
Cost of each drink = $1.50
a) Â So, the total number of Sandwiches and drinks purchased in Lunch
  = Number of sandwiches purchased + Number of drinks purchased
  = x + y
or, the total number of Sandwiches and drinks purchased  =  x + y
Now According to the question:
4 x  + 5 y = 120
To find possible pairs of solution take any arbitrary value for y .
Let y  = 4, then 4x  = 120 - 20 = 100
or, x = 100/4 = 25 ⇒  x  =25
Let y = 8, then  4x  = 120 - 420 = 80
or, x = 80/4 = 20  ⇒  x  = 20
Similarly, for y = 12, x  = 15
So, the three possible solution to the given equation  is : (25,4), (20,8) and  (15,12)