David Arnold wrote:

All,

Anyone have a nice technique to "strike out" the common primes using the color red?

\placeformula[-] \startformula \frac{12}{18}=\frac{2\cdot2\cdot3}{2\cdot3\cdot3}=\frac23 \stopformula

A simple solution: \defineoverlay[strikeme][{\color[red]{\bf/}}] \def\strikeout#1{\mframed[frame=off,background={foreground,strikeme}]{#1}} will draw bold red slashes over the numbers. They still seem a bit too thin too me , but you could use other bolder characters if needed. A more complex solution with metafun: \startuniqueMPgraphic{strikeme} draw (0,0)--(OverlayWidth,OverlayHeight) withpen pencircle scaled 3pt withcolor red; \stopuniqueMPgraphic \defineoverlay[strikeme][\uniqueMPgraphic{strikeme}] \def\strikeout#1{\mframed[frame=off,background=strikeme]{#1}} Usage: \startformula \frac{12}{18}=\frac{\strikeout{2}\cdot2\cdot\strikeout{3}}{\strikeout{2}\cdot\strikeout{3}\cdot3}=\frac23 \stopformula Mojca