а) (х+240)*3=1260

 3х+720=1260

3х=1260-720

3х=540

х=540:3

х=180

___________________

(180+240)*3=1260

б) х+(240*3)=1260

х+720=1260

х=1260-720

х=540

_________________

540+(240*3)=1260

(х+240)*3=1260

х=1260 :3

х=420

х=420-240

х=180

(180+240)*3=1260