$6.84 divided by 18= .38 which means 38 cents per pen
$8.40 divided by 30= .28 which means 28 cents per pen
so $8.40 for 30 pens is a better deal than 18 pens for $6.84 by ten cents.
HoHm : B means that starting at point B, you do a half-turn about m. This puts point B where A is. Continuing, this point is again allowed to to do a half-turn but this about o so that the point ends up at C.
The answer is Point C.<span />
Check the picture below.
what's the length? well, length = 3w - 6.