How do you multiply out brackets

This is simple as long as you remember FOIL:
First

Outside

Inside

Last

So, for example, let's multiply out (2x+1)(4x-3)

Multiply the first number from each bracket together: 2x times 4x = 8x²

Then the outside from each bracket: 2x times -3 = -6x

Then inside: 1 times 4x = 4x

And outside: 1 times -3 = -3

Then add all these together: 8x² -6x +4x-3

Final answer: 8x² -2x -3