Question

Alex stocks up for winter. He buys 32 cans of vegetables. He pays 80 cents per can for tomatoes and 40 cents per can for corn, for a total cost of $18.00. How many cans of corn does he buy?

Answer 1

Let x the the number of cans of tomatoes and 
      32 - x be the number of cans of corn

From the given that the total cost in buying all 32 cans of vegetables is $18 and the costs of each can of vegetables, we generate the equation,
 
                              18 = 0.80x + 0.40(32 - x)

Solving for x from the equation gives x = 13. Alex bought 32 - x cans of corn with a numerical value of 19. Thus, Alex bought 19 cans of corn. 

Answer 2

x + y = 32 --> x = 32 - y
now sub that into the other equation
80(32 - y) + 40y = 1800

Now you solve for y.
Once y is found, sub that back into the equation x + y = 32, and solve for x.

If you wish to check your answer, sub it back into the equations.
x + y = 32
13 + 19 = 32
32 = 32 (this works)

80x + 40y = 1800
80(13) + 40(19) = 1800
1040 + 760 = 1800
1800 = 1800 (this works) you are correct.

x = 13 and y = 19