Question

7 pens and 2 pencils cost £22
3 pens and 3 pencils costs £11
Find the cost of the pen

Answer 1

Answer:

cost of pen = 2.93333

cost of pencil = 0.73333

Step-by-step explanation:

let pens = x

& pencil= y

7x + 6y =66 --------- equation 1

3x + 21y =77 --------- equation 2

multply equation 1 by 3

and.

equation 2 by 7

21x + 6y = 66

21x + 21y = 77

- - -

then change the sign

so, postive sign change to negative and negative sign change to positive

so 21x cancle out

21x + 6y = 66

21x + 21y = 77

- - -

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

0 - 15y = -11

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

so -15y = -11

negative sign cancel out

so ,

15y = 11

y = 11/15

y = 0.73333

now put the value of y in any equation either 1 or 2

I put the value of y in 2nd equation

3x + 3(0.73333) = 11

3x = 11 - 2.19999

3x = 8.80001

x = 8.80001/3

x= 2.9333667