(х+240)*3=1260
Х+240=1260:3
Х+240=420
Х=420-240
Х=180
х + (240 * 3) = 1 260
Х+720=1260
Х=1260-720
Х=540
х + 240 = 1 260 * 3
Х+240=3780
Х=3780-240
Х=3540