We can think of the polygon as formed by two triangles.
The one on the top has a base of 4 units and and a height of 3 units, so its area is:
A(top) = (Base x Height)/2 = (4 x 3)/2 = 12/2 = 6 square units
The other triangle (upsidedown) has a base of 4 units and a height of 4 units, so it area is:
A(bottom) = (Base x Height)/2 = (4 x 4)/2 = 16/2 = 8 square units
Both triangles area is equal to the plygon area:
A(top) + A(bottom) = 6 + 8 = 14 square units
Answer:
Area of the polygon: 14 square units