Question

the cost of five pens and three pencils is 39 rupees. the cost of three pens and seven pencils is above 39 rupees. find the cost of a pen and that of a pen​

Answer 1

Step-by-step explanation:

let cost of one pen be 'x'

& cost of one pencil be 'y'

so our equations are

5x+3y=39

& 3x+7y=39

calculate both equations by substitution method

i e., (5x+3y=39)7

(3x+7y=39)3

so, 35x+21y=273

9x+21y=117

(-). (-). (-)

____________

26x= 156

x= 156/26

x=6

substitute x=6 in 1st equation

5(6)+3y=39

30+3y=39

3y=39-30

3y=9

y=9/3

y=3

the cost of one pen is 6 rupees

& the cost of one pencil is 3 rupees