Пошаговое объяснение:

3/7

(3*2)/(7*2) = 6/14

(3*5)/(7*5) = 15/35

(3*9)/(7*9) = 27/63

4/5

(4*4)/(5*4) = 16/20

(4*6)/(5*6) = 24/30

(4*8)/(5*8) = 32/40

7/11

(7*3)/(11*3) = 21/33

(7*5)/(11*5) = 35/55

(7*10)/(11*10) = 70/110

6/13

(6*3)/(13*3) = 18/39

(6*10)/(13*10) = 60/130

(6*15)/(13*15) = 90/195