Equations with Figures. HOW Tall is the Chair?

[@jesusistheonlyway1035]

suppose that x is the boy, y is the chair and z is the girl.
x+y=50cm+z
and
z+y=30cm+x
Add the equations together and you will get
(x+y)+(z+y)=50cm+30cm+z+x
when simplified 2y=80cm divide both sides by 2 and
y=40cm

[@guzmat]

right! nice