well, it seems to be just a sum of all quantities, now let's firstly convert the mixed fractions to "improper"and then add them up,
[tex]\bf \stackrel{mixed}{1\frac{7}{8}}\implies \cfrac{1\cdot 8+7}{8}\implies \stackrel{improper}{\cfrac{15}{8}}
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\stackrel{mixed}{1\frac{1}{2}}\implies \cfrac{1\cdot 2+1}{2}\implies \stackrel{improper}{\cfrac{3}{2}}\\\\
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\cfrac{15}{8}+\cfrac{3}{2}+\cfrac{7}{8}\quad \stackrel{LCD~8}{\implies }\quad \cfrac{15+12+7}{8}\implies \cfrac{34}{8}\implies \stackrel{simplified}{\cfrac{17}{4}}\implies 4\frac{1}{4}[/tex]
