Respuesta :

DJdumpling

Without loss of generosity, let x equal the number of sandwiches bought and y be the number of bottles of water bought. Since Eric bought 9 items,

                                                          x+y=9.


Also,

                                                      5x+2y=30.


This is because 5 is the price for the sandwiches and 2 is the price for the bottle of water.


sqdancefan

Answer:

  1. x + y = 9
  2. 5x +2y = 30

Step-by-step explanation:

You are given two bits of information that relate to the numbers of items:

  1. the total number of items purchased
  2. the total cost of items purchased

These two relations let you write two equations in the two unknowns, one for each relation.

Of course, the total cost is the cost of each multiplied by the number purchased. The variables are defined as the number purchased.

_____

Though the question doesn't ask for it, the solution can be found by elimination. Subtract twice the first equation from the second:

... (5x +2y) -2(x +y) = (30) -2(9)

... 3x = 12 . . . . . simplify

... x = 4 . . . . . . . divide by 3

... 4 + y = 9 . . . . substitute the value of x into the first equation

... y = 5 . . . . . . . subtract 4

The solution is (x, y) = (4, 5).

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