Question

Multiply.
(2+√7)(4-√7)

Answer 1

Multiply each term inside the first parentheses by each term inside the second parentheses, like FOIL

Answer 2

2(4) + 2(-sqrt(7)) + (sqrt(7))(4) + (sqrt(7))(-sqrt(7))

Answer 3

The first and last terms are regular numbers that you can then add together.
The two middle terms have radicals in them but they're both radical 7, so you can add them together