Use factor method to evaluate:

10y(6y + 21) ÷ (2y + 7)

$\dfrac{10y(6y + 21)}{(2y + 7)}\\[1em] \dfrac{10y \times 3(2y + 7)}{(2y + 7)}\\[1em] = \dfrac{30y(2y + 7)}{2y + 7}\\[1em] = \dfrac{30y\cancel{(2y + 7)}}{\cancel{(2y + 7)}}\\[1em] = 30y$

Hence, 10y(6y + 21) ÷ (2y + 7) = 30y