Then we can multiply the two binomials (9x2 - 16) and (5x + 6).
If instead we first multiplied (3x + 4) and (5x + 6), we would need to multiply (15x2 + 38x + 24) by (3x - 4), which would be an ugly calculation. Don't do that to yourself. You're a good person and deserve better.
Whichever way we do it, though, we should find the same final answer of