Question

РЕШИТЕ НАДО СРОЧНО!!!

Answer 1

1)
$left { {{x=8+5y} atop {2x+4y=30}} right.$ ⇒ $left { {{x=8+5y} atop 2(8+5y +4y=30)}} right.$ ⇒ $left { {{x=8+5y} atop {16+10y+4y=30}} right.$ ⇒ $left { {{x=8+5y} atop {14y=14}} right.$⇒$left { {{x=8+5y} atop {y=1}} right.$ ⇒$left { {{x=8+5} atop {y=1}} right.$ ⇒$left { {{x=13} atop {y=1}} right.$
2)
$left { {{y=2x-1} atop {7x-6y=-4}} right.$ ⇒$left { {{y=2x-1} atop {7x-6(2x-)=-4}} right.$ ⇒ $left { {{y=2x-1} atop {7x-12x+6+4=0}} right.$⇒
$left { {{y=2x-1} atop {-5x+10=0}} right.$⇒$left { {{y=2x-1} atop {x=2}} right.$⇒$left { {{y=3} atop {x=2}} right.$
3)
$left { {{5a-3(10-2a)=14} atop {b=10-2a}} right.$⇒$left { {{5a-30+6a=14} atop {b=10-2a}} right.$⇒$left { {{11a=44} atop {b=10-2a}} right.$⇒$left { {{a=4} atop {b=2}} right.$