Solve the following pair of linear equations by the method of substitution: $8x - 3y = 1$ and $34x - 3y = 14$.

Solve the following pair of equations: $2x + y = \frac{7xy}{3}, x + 3y = \frac{11xy}{3}$

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

The standard form of $2x = 5y$ is............

If $y = \frac{1}{2} x$ and $x + 2y = 8$,then $x = \dots$

$A$ motor boat can travel $30 \, km$ upstream and $28 \, km$ downstream in $7 \, hours$. It can travel $21 \, km$ upstream and return in $5 \, hours$. Find the speed of the boat in still water and the speed of the stream (in $km/h$).