Answer:
48f² - 110f + 63
Explanation:
Each term in the second factor is multiplied by each term in the first factor, that is
6f(8f - 9) - 7(8f - 9) ← distribute both parenthesis
= 48f² - 54f - 56f + 63 ← collect like terms
= 48f² - 110f + 63 ← in standard form