You can use Pick's theorem, where:
Area = Number of interior points (points inside the polygon) + [tex]\dfrac{1}{2}[/tex] · Number of boundary points (points on the polygon's perimeter) - 1
so:
1.Yellow:
Interior points = 3
Boundary points = 8
[tex]A=3+\dfrac{1}{2}\cdot8-1=3+4-1=\boxed{6\text{ units}}[/tex]
2. Red:
Interior points = 2
Boundary points = 10
[tex]A=2+\dfrac{1}{2}\cdot10-1=2+5-1=\boxed{6\text{ units}}[/tex]
