From the sum of $3a^2+5ab-7b^2$ and $11a^2-6ab+2b^2$, subtract $a^2-2ab-3b^2$.

The distance between two places Alok Nagar and Aroop Nagar is $(6\mathrm{x}-12) \mathrm{km}$. A bus which started from Alok Nagar covered $(2\mathrm{x}+3) \mathrm{km}$ in $1$ hour. Find the remaining distance the bus has to cover to reach Aroop Nagar.​

Sidharth has $₹\left(12x+25\right)$ in his account. If he withdraws $₹\left(8x-30\right)$ from his account, how much money is left in his account?

Mrs Choudhary took $₹\left(7x-50\right)$ with her for shopping. She spent $₹\left(2x+15\right)$ for groceries and $₹\left(3x-20\right)$ to buy fruits and vegetables. Find how much money was left with her.​

Find the value of the following expression for $x=3$:

 $2\mathrm{x}+1$