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

х/25 - 7/25 = 13/25х/25 = 13/25 + 7/25х/25 = 20/25х = 25*20/25х = 2053/63 - (22/63 - х/63) = 43/6322/63 - х/63 = 53/63 - 43/6322/63 - х/63 = 10/63х/63 = 22/63 - 10/63х/63 = 12/63х = 63*12/63х = 12