Question

решите методом подстановки​

Answer 1

$\displaystyle \left \{ {x+y=9} \atop {x-y=-1}} \right. \\\\\left \{ {{x+y=9} \atop {x=-1+y}} \right. \\\\-1+y+y=9\\y=5\\x=-1+5\\x=4\\(x,y)=(4,5)$