`a)` $\dfrac{110}{180}$`=`$\dfrac{110:10}{180:10}$`=`$\dfrac{11}{18}$

$\dfrac{-14}{54}$`=`$\dfrac{-14:2}{54:2}$`=`$\dfrac{-7}{27}$

$\dfrac{25}{270}$`=`$\dfrac{25:5}{270:5}$`=`$\dfrac{5}{54}$

MSC: `54`

$\dfrac{11}{18}$`=`$\dfrac{11.3}{18.3}$`=`$\dfrac{33}{54}$

$\dfrac{-7}{27}$`=`$\dfrac{-7.2}{27.2}$`=`$\dfrac{-14}{54}$

Giữ nguyên phân số $\dfrac{5}{54}$

`b)` $\dfrac{-51}{136}$`=`$\dfrac{-51:17}{136:17}$`=`$\dfrac{-3}{8}$

$\dfrac{-60}{108}$`=`$\dfrac{60:12}{108:12}$`=`$\dfrac{5}{9}$

$\dfrac{26}{-156}$`=`$\dfrac{-26}{156}$`=`$\dfrac{-26:26}{156:26}$`=`$\dfrac{1}{6}$

MSC: `72`

$\dfrac{-3}{8}$`=`$\dfrac{-3.9}{8.9}$`=`$\dfrac{-27}{72}$

$\dfrac{5}{9}$`=`$\dfrac{5.8}{9.8}$`=`$\dfrac{40}{72}$

$\dfrac{1}{6}$`=`$\dfrac{1.12}{6.12}$`=`$\dfrac{12}{72}$