S.O.S. Mathematics CyberBoard

Hello,
Forgive me for my english and will do my best to make this understandable.
I'm preparing for a real estate exam and having trouble with the math part of it. Unfortunately mathematics has never been my forte.

The question i was presented with is as follow:



When Branham brought his property he had a 20% down payment and
secured a 30 year loan at 7% interest. If his first month’s interest was
$787.50, how much did he pay for the property?
A. $135,000
B. $140,625
C. $168,750
D. $158,250


I'm sure there is a formula, given the down payment pewrcentage , monthly interest rate etc... , to solve this.
I figured that since it's $ 787.50 a month interests that will be $9450 a month and $283.500 at the end fo the 30 years loan term.
I tryed to figure out how much the 20% down payment was. I figured since one of those values ( A B C D ) is the price he payed for the house I tried them all=)
When i got to $ 140.625 I did 20% of this and came to$28.125 and i figured this was the down payment.
I now know the correct answear is $168.750 and oddly enough $140.625+28.125 = $168.750.
So is 28.125$ the down payment? if so how in the hell did i came up with the 20% down payment from $140.625?
Also how is it possible that Branham paid the property $168.750 when just of interest in 30 years it comes to $283.500?
Maybe I'm thinking of a mortage and a loan is a little different?

But If i ask a bank for a mortgage on a property valued at $168.750 and I'm only able to put down a 20% down payment , wich comes to $33.750.
168.750-33.750= $135.00 So i have a mortgage on $135.000 at 7% interest rate on 30 years.
Since I'm paying $283.500 in 30 years of interests alone at the end I will be paying this property $418.500 and not $168.750.
In other words are they asking me for the original price of the property before the interests? But i thought they asked for how much he will pay for the property and that can vary depending if Branham decides to pay off the loan at 2 years or at 5 years or at 15 years etc... The final price can change with a mortgage.
I'm confused if any can shed some light I will be greatfull.

Thanks in advanced and pardon for my spelling.

_________________
Walked over to a beggar...he gave me a quarter...