Đáp án+Giải thích các bước giải:

a, $\dfrac{75}{91}$ + $\dfrac{26}{24}$

= $\dfrac{5}{6}$ + $\dfrac{13}{12}$

= $\dfrac{23}{12}$

b, $\dfrac{42}{49}$ − $\dfrac{38}{56}$

= $\dfrac{6}{7}$ − $\dfrac{19}{28}$

= $\dfrac{5}{28}$.

c, $\dfrac{51}{72}$ + $\dfrac{55}{56}$

= $\dfrac{17}{24}$ + $\dfrac{55}{56}$

= $\dfrac{71}{42}$.

d, $\dfrac{1313}{1515}$ − $\dfrac{20}{25}$

= $\dfrac{13}{15}$ − $\dfrac{4}{5}$

= $\dfrac{1}{15}$.