Question

# The cost of a ball pen is Rs.5 less than half of the cost of fountain pen. Write this statement as a linear equation in two variables.

Hint: We can take the cost of ball pen as one variable and cost of fountain pen as another variable. By reading the given statement, we can understand that half of the cost of a fountain pen minus 5 gives the cost of a ball pen. We get the required equation by writing the relation in terms to two variables and simplifying.

Let ${\text{x = }}$ cost of fountain pen
And let ${\text{y = }}$ cost of ball pen
${\text{y = }}\dfrac{{\text{x}}}{{\text{2}}}{\text{ - 5}}$
${\text{y + 5 = }}\dfrac{{\text{x}}}{{\text{2}}} \\ {\text{2y + 10 = x}} \\$
Therefore, the required linear equation in 2 variables is ${\text{x = 2y + 10}}$.