first off, we convert the mixed fractions to "improper", and proceed getting their LCD from there, let's do so,
[tex]\bf 101\frac{3}{4}+33\frac{1}{4}+5\frac{1}{4}\\\\
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\stackrel{mixed}{101\frac{3}{4}}\implies \cfrac{101\cdot 4+3}{4}\implies \stackrel{improper}{\cfrac{407}{4}}
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\stackrel{mixed}{33\frac{1}{4}}\implies \cfrac{33\cdot 4+1}{4}\implies \stackrel{improper}{\cfrac{133}{4}}
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\stackrel{mixed}{5\frac{1}{4}}\implies \cfrac{5\cdot 4+1}{4}\implies \stackrel{improper}{\cfrac{21}{4}}\\\\
-------------------------------[/tex]
[tex]\bf \cfrac{407}{4}+\cfrac{133}{4}+\cfrac{21}{4}\impliedby \textit{clearly their LCD is 4}\implies \cfrac{407+133+21}{4}
\\\\\\
\cfrac{561}{4}\implies 140\frac{1}{4}[/tex]