1) 123х+458+254х+26=1238; 123х+254х=1238-26-458; 377х=754; х=754:377; х=2.
2) 2(6х+8)-3х=313; 12х+16-3х=313; 12х-3х=313-16; 9х=297; х=297:9; х=33
3) 708+139х+24+341х=1692; 139+341х=1692-24-708; 480=960; х=960:480; х=2
4) 3(7+4х)-8х=201; 21+12х-8х=201; 12х-8х=201-21;4х=180; х=180:4; х=45