In `DeltaABC`,
seg `BD` bisects `/_ABC`
`:.` by the theorem of angle bisector of a triangle,
`(AB)/(BC)=(AD)/(DC)`
`:.(x)/(x+5)=(x-2)/(x+2)`
`:.x(x+2)=(x-2)(x+5)`
`:.x^(2)+2x=x(x+5)-2(x+5)`
`:.x^(2)+2x=x^(2)+5x-2x-10`
`:.2x=3x-10 ` `:. 2x-3x=-10`
`:.-x=-10`
`:.x=10`
