The sum of two numbers is $8$. If the smaller number is $y$,then the larger number $x = \ldots \ldots \ldots \ldots$

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 by the cross-multiplication method:
$\frac{x}{5} - \frac{y}{4} = \frac{9}{40}$
$\frac{x}{3} - \frac{y}{2} = \frac{5}{12}$

Comparing the equation $x=4$ with the standard form $ax+by+c=0$,we get $b=\ldots \ldots \ldots$

There are some coins of $25$ paise and some coins of $50$ paise in a box. There are in all $20$ coins and they amount to Rs. $7$. Find the number of coins of $25$ paise and $50$ paise each.

Places $A$ and $B$ are $90\, km$ apart from each other on a highway. $A$ car starts from $A$ and another from $B$ at the same time. If they move in the same direction,they meet in $9$ hours and if they move in opposite directions,they meet in $\frac{9}{7}$ hours. Find the speeds of the cars.