yes, is subtraction, to get their "difference".
first off, let's convert the mixed fractions, to "improper", and then subtract.
[tex]\bf \stackrel{red~yarn}{9\frac{1}{5}}-\stackrel{blue~yarn}{3\frac{11}{25}}[/tex]
[tex]\bf -------------------------------\\\\
\stackrel{mixed}{9\frac{1}{5}}\implies \cfrac{9\cdot 5+1}{5}\implies \stackrel{improper}{\cfrac{46}{5}}
\\\\\\
\stackrel{mixed}{3\frac{11}{25}}\implies \cfrac{3\cdot 25+11}{25}\implies \stackrel{improper}{\cfrac{86}{25}}\\\\
-------------------------------\\\\
\cfrac{46}{5}-\cfrac{86}{25}\impliedby \textit{our LCD is 25}\implies \cfrac{(5\cdot 46)~~-~~(1\cdot 86)}{25}
\\\\\\
\cfrac{230~-~86}{25}\implies \cfrac{144}{25}\implies 5\frac{19}{25}[/tex]
