=20/60+15/60+12/60+48/60+40/60
=135/60
=9/4
\(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{8}{10}+\dfrac{20}{30}+\dfrac{15}{20}\)
\(=\dfrac{20}{60}+\dfrac{15}{60}+\dfrac{12}{60}+\dfrac{48}{60}+\dfrac{40}{60}+\dfrac{45}{60}\)
\(=\dfrac{180}{60}\)
\(=3\)
mình bổ xung \(\dfrac{15}{20}\) rồi nhé