first off, you'd want to put both fractions with the same denominator, and we simply do so by multiplying each other by the other's denominator.
[tex]\bf -\cfrac{7\cdot 5}{8\cdot 5}\implies -\cfrac{35}{40}\qquad \qquad\qquad \qquad -\cfrac{4\cdot 8}{5\cdot 8}\implies -\cfrac{32}{40}
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\textit{since there's no enough room for three fractions there,}\\\\
\textit{let's multiply each by 2, to make room for three fractions}[/tex]
[tex]\bf -\cfrac{35\cdot 2}{40\cdot 2}\implies -\cfrac{70}{80}\qquad \qquad \qquad \qquad -\cfrac{32\cdot 2}{4\cdot 20}\implies -\cfrac{64}{80}
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\boxed{-\cfrac{70}{80}}\qquad\qquad -\cfrac{67}{80}\qquad -\cfrac{66}{80}\qquad -\cfrac{65}{80}\qquad\qquad \boxed{-\cfrac{64}{80}}[/tex]
