Two years ago,the sum of the ages of a mother,father,and two daughters was $40$ years. After three years,what will be the sum of their ages?

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.

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.

Two straight paths are represented by the equations $x-3y=2$ and $-2x+6y=5$. Check whether the paths cross each other or not.

$A$ line $x-2y=2$ intersects the $Y$-axis at..........

Solve the following pair of equations by the method of cross multiplication:
$x + y - (a + b) = 0$
$ax - by - (a^2 - b^2) = 0$