Four-fifths of a number is greater than three-fourths of the number by $4$. The number is

The sum of three consecutive integers is $51$. The middle one is

The number of boys and girls in a class is in the ratio $7:5$. The number of boys is $8$ more than the number of girls. The total class strength is

Subtract $4a^2+5b^2-6c^2+8$ from $2a^2-3b^2-4c^2-5$

Find the product of

$\left(4a+5b\right)\left(5a-6b\right)$

Find the product $\left(6x^2-x+8\right)\times \left(x^2-3\right)$.