3) Вычислите: 5/11 + 4/11; 12/19 − 4/19; 5/11 + 4/7; 4/9 − 2/11; 8/15 + 3/5; 9/25 − 1/4; 7/30 · 6/21; 4/12 · 18/20; 21/25 · 15/42; 3/20 : 17/10; 8/11 : 4/99; 16/17 · 7/34.

\(\frac5{11}+\frac4{11}=\frac9{11}\).

\(\frac{12}{19}-\frac4{19}=\frac8{19}\).

\(\frac5{11}+\frac47=\frac{35+44}{77}=\frac{79}{77}=1\frac2{77}\).

\(\frac49-\frac2{11}=\frac{44-18}{99}=\frac{26}{99}\).

\(\frac8{15}+\frac35=\frac8{15}+\frac9{15}=\frac{17}{15}=1\frac2{15}\).

\(\frac9{25}-\frac14=\frac{36-25}{100}=\frac{11}{100}\).

\(\frac7{30}\cdot\frac6{21}=\frac1{15}\).

\(\frac4{12}\cdot\frac{18}{20}=\frac3{10}\).

\(\frac{21}{25}\cdot\frac{15}{42}=\frac3{10}\).

\(\frac3{20}:\frac{17}{10}=\frac3{20}\cdot\frac{10}{17}=\frac3{34}\).

\(\frac8{11}:\frac4{99}=\frac8{11}\cdot\frac{99}4=18\).

\(\frac{16}{17}\cdot\frac7{34}=\frac8{17}\cdot\frac7{17}=\frac{56}{289}\).