Raphael paid 636 for camera during a 60% off sale with the cameras regular price

60% off means u paid 40%

40% of the regular price = 636
0.40x = 636
x = 636/0.40
x = 1590 <==

Your question needs some rewording.  How does this sound?  "Raphael paid $636 for camera during a 60% off sale.  The camera's regular price is x.  Find this price."

If the price is 60% lower than usual, Raphael is paying only (100% - 60%), or 40%, for the camera.

Thus, 0.40x = $636.  Divide both sides of this eq'n by 0.40 to find the original price of the camera.

x = $636/0.40 = ?

How about we consider our specimen space. We have 3 coins, each with 2 conceivable results. This gives us 2^3=8 particular results. 
Ω={HHH,HHT,HTH,HTT,THH,THT,TTH,TTT}Ω={HHH,HHT,HTH,HTT,THH,THT,TTH,TTT} 
We realize that the coins are reasonable, so it can be seen that each of these results is similarly likely. That is, every individual grouping has a likelihood equivalent to one over the span of the specimen space, or 1/8. 
Presently we can just tally. There are 4 successions that incorporate no less than 2 heads: 
{HHH,HHT,HTH,THH}{HHH,HHT,HTH,THH} 
The likelihood of any of these occasions happening is equivalent to the entirety of the individual probabilities of these occasions happening, so the likelihood of no less than two heads is 4/8 or 1/2.