Comparing the equation $y = -3$ with the standard form $ax + by + c = 0$,we get $a = \dots$

Are the following pair of linear equations consistent? Justify your answer.
$-3x - 4y = 12$
$3x + 4y = 12$

Which of the following is a solution of the linear equation in two variables $x - 2y = 4$?

Solve the following pairs of linear equations: $\frac{2}{x} + \frac{3}{y} = \frac{9}{xy}, \quad \frac{4}{x} + \frac{9}{y} = \frac{21}{xy} \quad (x \neq 0, y \neq 0)$

For which values of $p$ and $q$ will the following pair of linear equations have infinitely many solutions?
$4x + 5y = 2$
$(2p + 7q)x + (p + 8q)y = 2q - p + 1$

$6$ students of class $X$ took part in the Ramanujan Competitive Examination. The number of girl participants is $2$ less than the number of boy participants. Find the number of girls and the number of boys who took part in the examination using a graph.