i THINK i got the first part.
is it:
<a href="http://www.codecogs.com/eqnedit.php?latex=\frac{20-DC}{10} = \frac{x}{100}" target="_blank"><img src="http://latex.codecogs.com/gif.latex?\frac{20-DC}{10} = \frac{x}{100}" title="\frac{20-DC}{10} = \frac{x}{100}" /></a>
<a href="http://www.codecogs.com/eqnedit.php?latex=\text{Therefore} \\ DC = 20 - \frac{x}{10}" target="_blank"><img src="http://latex.codecogs.com/gif.latex?\text{Therefore} \\ DC = 20 - \frac{x}{10}" title="\text{Therefore} \\ DC = 20 - \frac{x}{10}" /></a>
And I have no clue about the next part.