Since the base is a triangle its area is given as:
[tex]A=\frac{1}{2}bh[/tex]
In this case the lenght of the base of the triangle is 3 and its height is 4, then the area of the base is:
[tex]A=\frac{1}{2}(3)(4)=\frac{3\cdot4}{2}[/tex]
Therefore the answer is the third option.
