Question

Help pleas mor points!

Answer 1

Answer
(a) sandwich cost £2
(b) cookie cost £1

let sandwiches be x
let cookies be y

3x + 2y=8……(1)
7x +2y=16……(2)

multiple equation (2) throughout by (-)

3x + 2y=8
-7x -2y= -16

Add both equations

-4x + 0= -8

-4x = -8
divide both side by -4

-4x/-4 = -8/-4

x = 2

so the cost of sandwich is £2

substitute x=2 into equation (1)

3x + 2y=8……(1)

3(2) + 2y=8

6 + 2y=8

so if we transpose

2y=8-6

2y=2

divide both side by 2

2y/2=2/2

y = 1

and the cost of cookie is £1

Answer 2

Sandwich = 2

Cookie = 1

Explanation:

Let

• cost of sandwiches = x
• cost of cookies = y

This would mean :

3x + 2y = 8 and 7x + 2y = 16

Because we have two similar terms in the equations, (2y) we can subtract the two equations from each other cancelling out the terms resulting in us having one term that we can solve for. This is known as the elimination method

7x + 2y = 16

- 3x + 2y = 8

-----------------------

4x + 0y = 8

==> 4x = 8

==> x = 2

We can now plug in the value of x into one of the equations and solve for y

==> 7x + 2y = 16

==> 7(2) + 2y = 16

==> 14 + 2y = 16

==> 2y = 2

==> y = 1

We can conclude that the cost of a sandwich is 2 and the cost of a cookie is 1