N1 а) 42/39х1/42х39/60= б) 101/102х102/103х103/104= в) 3/8х8/13х13/18= n2 а) 25х7/30= б) 32х11/48= в) 13/15х6= г) 7/20х15=

№1.
42/39 * 1/42* 39/60 = (42*1*39) /(39*42*60)= (1*1*1)/(1*1*60) = 1/60

101/102 *  102/103 * 103/104 = (101*102*103)/ (102*103*104) =
= (101*1*1)/(1*1*104) = 101/104

3/8 *8/13 * 13/18 = (3*8*13)/ (8*13*18) = (1*1*1)/(1*1*6)= 1/6

№2.
25  *  7/30  = 25/1  *  7/30 = (25*7)/(1*30)=
=(5*7)/ (1*6) = 35/6 = 5 5/6

32  *  11/48 = (32*11)/(1*48) =  (2*11) /( 1*3) =
= 22/3=  7  1/3

13/15  * 6  =  (13*6)/(15*1)= (13*2)/ (5*1) = 
= 26/5 = 5  1/5

7/20  * 15  = (7*15)/ (20*1) = ( 7*3)/(4*1)=
= 21/4 = 5  1/4