This shape is basically a rectangle and a triangle, so the area will be
Area=(area of rectangle)+(area of triangle)
We know the area of the rectangle so we can just plug that in
Area=3+(area of triangle)
The formula for the area of a rectangle is
A(rectangle)=l*w where l=length and w=width
plug in the data we know
3=l*2
divide both sides by 2
3/2=l
1.5=l
So the length is 1.5miles. Now that we have this, we can solve for the area of the triangle.
The formula for the area of a triangle is
A(triangle)=1/2b*h where b=base and h=height
The height of the triangle is (4-2=2) 2 miles. Now let's solve for the area...
A(triangle)=1/2*1.5*2
A(triangle)=1.5mi²
So
Area=3+1.5
Area=4.5mi²