Simplifying
(3x + 9)(2x + 5)

Reorder the terms:
(9 + 3x)(2x + 5)

Reorder the terms:
(9 + 3x)(5 + 2x)

Multiply (9 + 3x) * (5 + 2x)
(9(5 + 2x) + 3x * (5 + 2x))
((5 * 9 + 2x * 9) + 3x * (5 + 2x))
((45 + 18x) + 3x * (5 + 2x))
(45 + 18x + (5 * 3x + 2x * 3x))
(45 + 18x + (15x + 6x2))

Combine like terms: 18x + 15x = 33x
(45 + 33x + 6x2)