х/25-7/25=13/25; 53/63-(22/63-х/63)=43/63

х/25 - 7/25 = 13/25
х/25 = 13/25 + 7/25
х/25 = 20/25
х = 25*20/25
х = 20

53/63 - (22/63 - х/63) = 43/63
22/63 - х/63 = 53/63 - 43/63
22/63 - х/63 = 10/63
х/63 = 22/63 - 10/63
х/63 = 12/63
х = 63*12/63
х = 12