Question

a person spent 564 in buying pens and pencils if cost of eaach pen is 7 and each pencil is 3 and if the total number of things bought was 108,how many of each type did he buy?

Answer 1

Let a pen be x ,pencil be y.

so: if i price of 1 pen is 7 and price of pencil is 3.

7x +3y= 564 ( equation 1)

x + y = 108 ( equation 2)

make 1 term similiar in both equations ,lets make the term y = 3y to get a similiar term.

then,(second equation *3)

=3x+3y=324 (lets name it equation 3)

apply the rule: different signs add,same signs substract.

we now have the similiar term 3y,here the term 3y is positive in both equations hence substract the two equations ,first cancel off the 3y in both equations and find x.

7x+3y=564 (equation 1)

3x+3y=324(equation 2)

(1-2)

7x-3x=564 - 324

4x/4 = 240/4

x=60

substitute x=60 in equation 2 ,

60+Y=108

Y=108 - 60

Y = 48

THEREFORE HE HAS BOUGHT 60 PENS AND 48 PENCILS.