Lynn street, allen street, and route 11 form the boundaries of a triangular forest, as shown in the map below.

There are 2 triangles there. So the formula for a triangle is BxH/2. So base of 36km x 15km = 540/2= 270km squared.
Then the second triangle 20km x 15 km=300/2=150km squared.
Next add the two triangles together so
270km squared + 150km squared= 420km squared.
420km squared is your answer

Do you remember how to find the area of a triangle ?

Is the area (1/2) (base) x (height) ?

On the map, the base and the height are conveniently labeled for you. 
The base is (20 + 36) = 56 km, and the height is 15 km.

I'm sure you can handle it from there, and earn yourself 5 points.