Question 47744
Do you mean
{{{ P(x) = 2x^4 + x^3 + 12 }}}

If so, the question is a straightforward exercise in evaluating functions.
{{{ P(-1/2) = 2(-1/2)^4 + (-1/2)^3 + 12 }}}
What I have done is to replace every instance of x with (-1/2)
This gives
2(-1/2)^4 + (-1/2)^3 + 12
= 2(1/16) + (-1/8) + 12
= 1/8 - 1/8 + 12
= 12