6х+4у-4х=21-9⇒2х=4у=12⇒х+2у=6⇒х=6-2у--------------------------------------------------------2х+6х+5у=3-10⇒8х+5у=-7---------------------------------8(6-2у)+5у=-7----------------------48-16у+5у=-7---------------------11у=-55------------у=5-------х=6-2*5=6-10=-4--------------------Удачной учебы :з