**The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement.**

**(Take the cost of a notebook to be Rs x and that of a pen to be Rs y).**

Solution:

Let the cost of the notebook be ‘x’ and the cost of the pen be ‘y’

Then by the given data, x = 2y

This can be written as x – 2y = 0

**Express the following linear equations in the form ax + by + c = 0 and indicate the values of a, b and c in each case:**

**(i) 2x + 3y = 9.3**

Solution:

2x + 3y – 9.3 = 0

Therefore, a = 2 , b = 3 , c = – 35

**(ii) x – ^{y}/_{5} – 10 = 0**

Solution:

a = x ; b = – ^{1}/_{5} ; c = -10

**(iii) –2x + 3y = 6**

-2x + 3y – 6 = 0

a = -2 ; b = 3 ; c = -6

**(iv) x = 3y**

x – 3y = 0

Thus, a = 1 ; b = -3 ; c = 0

**(v) 2x = –5y**

2x + 5y = 0

a = 2 and b = 5 , c = 0

**(vi) 3x + 2 = 0**

3x + 0.y + 2 = 0

a = 3 ; b = 0 ; c = 2

**(vii) y – 2 = 0**

0.x + y – 2 = 0

a = 0 ; b = 1 and c = -2

**(viii) 5 = 2x**

– 2x + 5 = 0

– 2x + 0.y + 5 = 0

Thus, a = -2 ; b = 0 and c = 5

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