13х + 12х + 15 = 240
25х = 240-15
25х = 225
х = 9
(14х - 2х) : 17 = 312
12х : 17 = 312
12х = 312 * 17
12х = 5304
х = 5304 : 12
х = 442
13х + 12х + 15 = 240
25х = 240-15
25х = 225
х = 9
(14х - 2х) : 17 = 312
12х : 17 = 312
12х = 312 * 17
12х = 5304
х = 5304 : 12
х = 442
25х+15=240
25х=240-15
25х=225
х=225:25
х=9
(14х - 2х):17= 312
12х:17=312
12х=312*17
12х=5304:12
х=442