Question

3pens, 4 note books together cost rs.110 and 7 pens 5 note books cost rs.170 . find the cost of each pen and each note book

Answer 1

let x be the cost of each pen,
and y be the cost of each note books,
3x+4y=110
by multiplying first equation with 7 then it will be,
21x+28y=770
7x+5y=170
and now this equation with 3 then the equation will be,
21x+15y=510
now by changing sec. equation sign we will solve this
by solving this ,
21x+28y=770
21x+15y=510
- - -
0+13y=260
y=260/13 =20
then by putting y=20,
3x+4*20=110
3x=30
x=10
thus cost of pen is 10 and notebook is 20