A sequence of transformations maps ∆ABC onto ∆A″B″C″. The type of transformation that maps ∆ABC onto ∆A′B′C′ is a reflection
.

When ∆A′B′C′ is reflected across the line x = -2 to form ∆A″B″C″, vertex
of ∆A″B″C″ will have the same coordinates as B′.