A) Quy đồng mẫu số chung 48
$\frac{3}{8}$ +$\frac{1}{4}$- $\frac{5}{12}$
= $\frac{18}{48}$ + $\frac{12}{48}$ - $\frac{20}{48}$
= $\frac{18+12- 20}{48}$
= $\frac{10}{48}$ = $\frac{5}{24}$
B) Quy đồng mẫu số chúng 24
$\frac{-1}{8}$ + $\frac{-5}{3}$
= $\frac{-1}{8}$ - $\frac{5}{3}$
= $\frac{-3}{24}$ - $\frac{40}{24}$
= $\frac{-3- 40}{24}$
= $\frac{-43}{24}$
C) Tách $\frac{-56}{49}$= $\frac{-8}{7}$ x $\frac{7}{7}$
$\frac{-7}{8}$ x $\frac{-56}{49}$
= $\frac{-7}{8}$ x $\frac{-8}{7}$ x $\frac{7}{7}$
= $\frac{7}{7}$ =1
