4) 2_7+1_3 5)15_18+2_3. 6)5_6+2_3. 7) 5_6+2_9. 8)1_4+2_5 умоляю

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[tex] \frac{2}{7} + \frac{1}{3}
 множитель 3 и 7 => \frac{6}{21} + \frac{7}{21} = \frac{13}{21}
15/18 + 2/3=15/18+12/18=27/18=9/6=3/2=1,5
5/6+2/9=15/18+4/18=1 1/18
1/4+2/5=5/20+8/20=13/20