440...marked down by 30% means u pay 70%
70% of 440 = 0.70(440) = 308
308 ..marked down by 10% means u pay 90%
90% of 308 = 0.90(308) = 277.20 <== price after markdowns
^ means to the power of or exponent
logb(x) = y is b^y = x
When you divide 287 by 68, when it is not rounded, you will get 4.22058823529... (repeated decimal), but when you round it, you can either get the following: 4.22, 4.2, or 4 (choose which ever you want to pick out of these rounded forms.)
Hope this helped!
Nate