Expand (x+4)(x+3).

To answer this you multiply everything in the left bracket by everything in the right bracket, so rewrite the equation as x(x+3)+4(x+3). Then you can expand each more easily:

x(x+3) = x²+3x
4(x+3) = 4x+4×3 = 4x+12

Then add the answers and collect like terms:

x²+3x+4x+12 = x²+7x+12