реши уравнение 2*x=840 x*5+80=690 (708-x)+130 =500 x/3-18=12 x/19=19 120/(25-x)=10

2*х=840                         (708-х)+130=500                   х/19=19
х=840/2                         708-х=500-130                      х=19*19
х=420                            708-х=370                             х=361
                                      х=708-370
                                       х=338                                                                                                             
х*5+80=690                   х/3-18=12                               120/(25-х)=10
х*5=690-80                    х/3=12+18                               25-х=120/10
х*5=610                         х/3=30                                      25-х=12
х=610/5                         х=30/3                                      х=25-12
х=122                            х=10                                         х=7