Question

romila went to a stationary shop and purchased 2 pencils and 3 erasers for Rs.9. her friend Sonali saw the new variety of pencils and erasers with romila, and she also bought 4 pencils and 6 erasers of the same kind for Rs.18 .By substitution method

Answer 1

let the pencil be x and erasers be y
romila bought

2x+3y=9....
x=9-3y÷2...........equation 1


her friend bought 4 pencils and 6 erasers

that is ... 4x +6y = 18...... equation 2

substitute the value of x in equation 2

4(9-3y)÷2+ 6y =18

36-12y÷2 + 6y = 18

-12y+6y÷2 =18-36

-6y ÷ 2 = -18
-6y = -18÷2
-6y = -9
y = -9÷(-6)
y = 3÷2


substitute value of y in equation 1
x= 9-3(3÷2)÷2