РЕШИТЕ СИСТЕМЫ ЛИНЕЙНЫХ УРАВНЕНИЙ, ПОЖАЛУЙСТА!!! СРОЧНО НАДО!!!

первое

m - 3n = 8,
2m - 3n = 10;

m = 8 + 3n,
2m - 3n = 10;

m = 8 + 3n,
2*(8 + 3n) - 3n = 10;

m = 8 + 3n,
16 + 6n - 3n = 10;

m = 8 + 3n,
n = -2;

m = 8 + 3*(-2),
n = -2;

m = 2,
n = -2.

второе

3x + 4y = 10,
4x + 3y = 5;

x = (10 - 4y)/3,
4x + 3y = 5;

x = (10 - 4y)/3,
4*((10 - 4y)/3) + 3y = 5;

x = (10 - 4y)/3,
(40 - 16y)/3 + 3y = 5;

x = (10 - 4y)/3,
40 - 16y + 9y = 15;

x = (10 - 4y)/3,
y = 25/7;

x = (10 - 4*(25/7))/3,
y = 25/7;

x = (-30/7)/3,
y = 25/7;

x = -10/7,
y = 25/7.