To convert the given expression into standard form, we need to expand the expression on the left side and rearrange the terms on the right side.
Expanding the left side:
(x+3)(x-4) = x(x) + x(-4) + 3(x) + 3(-4)
= x^2 - 4x + 3x - 12
= x^2 - x - 12
So, the equation becomes:
x^2 - x - 12 = 5