Решите систему уравнений:( номера 5 и 6)

$\left \{ {{3(2a-1)+6(7-b)=51} \atop {2(b+6)-7(1+6b)=-39}} \right. \\\ \left \{ {{6a-3+42-6b=51} \atop {2b+12-7-42b=-39}} \right. \\\ \left \{ {{6a-6b=12} \atop {-40b=-44}} \right. b=1.1 \\\ a-b=2 \\\ a=b+2=1.1+2=3.1$
Ответ: (3,1; 1,1)
$\left \{ {{ \frac{3x-2y}{4}- \frac{4x+5}{3}=-5 } \atop { \frac{6x-5y}{2}+ \frac{2x+y}{5}=9 }} \right. \\\ \left \{ {{ 3(3x-2y)- 4(4x+5)=-60 } \atop {5(6x-5y)+ 2(2x+y)=90 }} \right. \\\ \left \{ {{ 9x-6y- 16x-20=-60 } \atop {30x-25y+ 4x+2y=90 }} \right. \\\ \left \{ {{ -7x-6y=-40 } \atop {34x-23y=90 }} \right. \\\ \left \{ {{ 161x+138y=920 } \atop {204x-138y=540 }} \right. \\\ 365x=1460 \\\ x=4 \\\ 161x+138y=920 \\\ y= \frac{920-161\cdot4}{138} =2$
Ответ: (4; 2)