(3x + 6) (5x +4)
I need help I don’t understand

[tex](3x + 6)(5x + 4) \\ [/tex]
[tex] = 3x(5x + 4) + 6(5x + 4)[/tex]
[tex] = 15 {x}^{2} + 12x + 30x + 24[/tex]
[tex] = 15 {x}^{2} + 42x + 24[/tex]