Question

решите систему уравнений:
20 = 5 Х + Y
(40-5x)/ 5 =(20-3Y)/1   
х= ?,у =?

Answer 1

$left { {{20=5x+y} atop { frac{40-5x}{5}=20-3y}} right.$
$left { {{y=20-5x} atop { frac{40-5x}{5} =20-3(20-5x)}} right.$
$left { {{y=20-5x} atop {40-5x=100-15(20-5x)}} right.$
$left { {{y=20-5x} atop {40-5x=100-300+75x}} right.$
$left { {{y=20-5x} atop {40-5x=-200+75x}} right.$
$left { {{y=20-5x} atop {-80x=-240}} right.$
$left { {{y=20-5x} atop {x=3}} right.$
$left { {{y=20-5*3} atop {x=3}} right.$
$left { {{y=5} atop {x=3}} right.$