Ineed to know the area of this irregular shape.

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

What do you mean by that?