f(x) = 4x+3
f(-1/2) = 4(-1/2)+3
f(-1/2) = -2+3
f(-1/2) = 1
-----------------------
g(x) = 3x
g(-1/2) = 3(-1/2)
g(-1/2) = -3/2
-----------------------
Replace x with -1/2 to go from
f(x)*g(x)
to
f(-1/2)*g(-1/2)
So you'll multiply the results of 1 and -3/2 to get 1*(-3/2) = -3/2
-----------------------
The final answer is -3/2