After $x$ years,the sum of the ages of Sachin and Sehwag will be $y$ years,then the sum of the ages before $3$ years was $\ldots \ldots \ldots \ldots$ years.

The pair of equations $y=0$ and $y=-7$ has

Susan invested a certain amount of money in two schemes $A$ and $B,$ which offer interest at the rate of $8 \%$ per annum and $9 \%$ per annum,respectively. She received $Rs.\, 1860$ as annual interest. However,had she interchanged the amount of investments in the two schemes,she would have received $Rs.\, 20$ more as annual interest. How much money did she invest in each scheme?

Draw the graphs of the pair of linear equations $x-y+2=0$ and $4x-y-4=0$. Calculate the area of the triangle formed by the lines so drawn and the $x$-axis (in sq. units).

For which values of $a$ and $b$ does the following pair of linear equations have infinitely many solutions?
$x + 2y = 1$
$(a - b)x + (a + b)y = a + b - 2$

Four years ago,the sum of the ages of four persons was $40$ years. After two years,the sum of the ages of the same four persons will be ............ years.