502 - (217 - х) = 421
502-217+х=421
х=421+217-502
х=136
871 - (х + 157) = 385
871-х-157=385
-х=385+157-871
-х=-329
х=329
502 - (217 - х) = 421
502-217+х=421
х=421+217-502
х=136
871 - (х + 157) = 385
871-х-157=385
-х=385+157-871
-х=-329
х=329