now, we know there are 3 and 3/4 bags in the cupboard, and each one of them weights 5 and 1/2 lbs, so the amount in the cupboard is just their product.
now, let's firstly convert the mixed fractions to "improper" and do the product after,
[tex]\bf \stackrel{mixed}{5\frac{1}{2}}\implies \cfrac{5\cdot 2+1}{2}\implies \stackrel{improper}{\cfrac{11}{2}}
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\stackrel{mixed}{3\frac{3}{4}}\implies \cfrac{3\cdot 4+3}{2}\implies \stackrel{improper}{\cfrac{15}{4}}\\\\
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\cfrac{11}{2}\cdot \cfrac{15}{4}\implies \cfrac{165}{8}\implies \stackrel{lbs}{20\frac{5}{8}}[/tex]