2g-4p=-9 ; 2t-4g=-7; 2p-4t=2 тогда p+g+t- скоклько выйдет

2g-4p=-9        +3t                                                    2g+3t-4p=3t-9
                                                                              +
2t-4g=-7        +3p в обе части уравнения             2t-4g+3p=3p-7
                                                                              +
2p-4t=2         +3g                                                    2p-4t+3g=2+3g
                                                                              =
                                                                                p+g+t=3(p+g+t)-14
(p+g+t)-3(p+g+t)=-14
(p+g+t)(1-3)=-14
-2(p+g+t)=-14
p+g+t=7