Question

Karen is seven years older than suzanne.Four years ago,karen was twice as old as suzanne was.How are they now?

Answer 1

$x-\ Karen's\ age\\\\ y-\ Suzanne's\ age\\\\ \left \{ {{x=y+7} \atop {x-4=2(y-4)}} \right.\\\\ \left \{ {{x=y+7} \atop {x-4=2y-8}} \right.\\\\ \left \{ {{x=y+7} \atop {x=2y-4}} \right.\\\\y+7=2y-4\ \ \ | subtract\ 2y\\\\ -y+7=-4\ \ \ | subtract\ 7\\\\ -y=-11\ \ \ | multiply\ by\ -1\\\\ y=11\\\\ x=11+7=18\\\\ Now\ Karen\ is\ 18\ years\ old \ and\ Suzanne\ is\ 11\ years\ old.$