a, 2/5 + 2/3 + 3/4=109/60
b, 8/5 - 18/27=14/15
c, 2/7 + 5/9=53/63
d, 5/16 + 7/16 + 3/24=7/8
e, 2/3 - 4/15=2/5
\(a,\dfrac{2}{5}+\dfrac{2}{3}+\dfrac{3}{4}=\left(\dfrac{2}{5}+\dfrac{2}{3}\right)+\dfrac{3}{4}=\dfrac{16}{5}+\dfrac{3}{4}=\dfrac{109}{60}\)
\(b,\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{216}{135}-\dfrac{90}{135}=\dfrac{126}{135}=\dfrac{14}{15}\)
\(c,\dfrac{2}{7}+\dfrac{5}{9}=\dfrac{18}{63}+\dfrac{35}{63}=\dfrac{53}{63}\)
\(d,\dfrac{5}{16}+\dfrac{7}{16}+\dfrac{3}{24}=\left(\dfrac{5}{16}+\dfrac{7}{16}\right)+\dfrac{3}{24}=\dfrac{3}{4}+\dfrac{3}{24}=\dfrac{7}{8}\)
\(e,\dfrac{2}{3}-\dfrac{4}{15}=\dfrac{10}{15}-\dfrac{4}{15}=\dfrac{6}{15}=\dfrac{2}{5}\)
