Question

решите систему уравнений {3х+4y=55; 7x-y=56

Answer 1

$left { {{3x+4y=55} atop {7x-y=56}} right. left { {{3x+4y=55} atop {28x-4y=224}} right. \ 3x+4y=55 \ + \ 28x-4y=224 \ 31x=279 \ x=9 \ 63-y=56 \ y=7 \ left { {{y=7} atop {x=9}} right.$