triangle

1/2*4*13=26

area of shaded region is called x.

Total area minus blank region= x

lets call area of blank region y

lets call total area z

\(z-y=x\)

\(z = (12\times9)/2\)

\(z=54\)

\(y=\frac{12\times5}{2}\)

\(y=30\)

Plug them in to get

\(54-30=x\)

\(x=24\)

Here's another way: 

The area of the 2 triangles is \(12 \times (5 + 4) \div 2 = 54 \)

The area of the white triangle is \(12 \times 5 \div 2 = 30\)

This means that the area of the shaded region is \(54 - 30 = \color{brown}\boxed{24}\)