Question

помогите решить 985(1и3)

Answer 1

(5/21  +  2/15)+ 2/21=  7/21  + 2/15= 1/3  +  2/15 = 5/15  +  2/15=  7/15
 
(7/30  +  8/45)+(2/45  +  1/30)= 8/30  +  10/45 = 24/90  +  20/90 =  44/90 = 22/45