Answer
$$3(2x+1)(5x-7).$$
Work Step by Step
For the polynomial
$$
30x^2-27x-21=3(10x^2-9x-7)
$$
we check the factors of $ac=10(7)=70$. The only factors that can give the right middle term are $-14$ and $5$, as follows
$$30x^2-27x-21=3(10x^2-9x-7)=3(2x+1)(5x-7).$$
