Simplify the following.
3((\( \frac{6}{3} \))x² − 21x + 18) − 6(x² + 5x − 18)
The simple interest on a certain sum for 7 \( \frac{2}{3} \) years at the rate of 5.4% per annum is ₹4,347. What will be the amount payable on the same sum at the rate of 7.5% per annum simple interest in 4 \( \frac{4}{5} \) years?