We know that the perimeter of a rectangle is twice the length, plus twice the width.
P = 2L + 2W
We also know that the perimeter is 156.
P = 156
Finally, we know that the width is 12 less than the length.
W = L - 12.
The next thing that we do is substitute the information that we have into the original equation:
P = 2L + 2W
156 = 2L + 2(L - 12)
From this point we start to solve
156 = 2L + 2L - 24 <---we multiplied the '2' through the parenthesis
156 + 24 = 2L + 2L - 24 + 24
180 = 2L + 2L <--- getting like terms on same sides
180 = 4L <---combining like terms
180/4 = 4L/4 <--- getting like terms on same sides
45 = L <---now we have a value for L
Now we take the known value for L and substitute it in to our equation for W
W = L - 12
W = 45 - 12
W = 33
So now we have Length = 45 and Width = 33.
9 is 18% of 50. So, 50 percent also written as 50% means 50 out of 100 parts. Since there are exactly two 50s in 100, fifty percent is the same number as one half. 50 percent=0.5 in but as a fraction, its 1/2.
2: Midpoint of segment AC is given as B3: Given4: Knowing that AC~=BC, AC~= DE
The formula for circumference is

.
To express the circumference exactly, plug the diameter in for

and put the

symbol in front of it. Don't multiply. This expresses the exact circumference.
Say you have the diameter of 17.
You can express the circumference with 17

.
This looks hard... good luck ! :D