Answer :
Let the first term of both the terms be
and last term be 
Now, by using the mid point formula to find the mid point of the segment -

Now, by substituting the values of both x and y -

Adding -7 and 6 -

Now, move the negative in front of the fraction -

The area of the actual castle would be 388,800 sq. ft.
We would multiply each of the sides of the scale model both by 180 to find the side lengths of the actual castle.
So...
180 x 4 = 720
180 x 3 = 540
If Area is equal to Length Times Width, all thats left to do is to multiply the two sides together.
720 x 540 = 388,800
Hope this helped! :D
This is simply a question about ratios. This ratio means that for every 1 cm on the map, there are 12 km in actuality. You can set this problem up in fractions:
1 cm 12 cm
-------- = ----------
12 km x
To solve for x, we cross-multiply, for the moment ignoring units. Remember, your answer will be in km.
1*x=12*12
x=144
If x=144, then for 12 cm, there are 144 km.