If ∆ABC and ∆DBC are on the same base BC, AB = DC and AC = DB (Fig. 6.21), then which of the following gives a congruence relationship?

By which of the following criterion two triangles cannot be proved congruent?

If ∆PQR is congruent to ∆STU (Fig. 6.20), then what is the length of TU?

Fill in the blanks to make the statements true.

The ________ triangle always has altitude outside itself.

Fill in the blanks to make the statements true.

The sum of an exterior angle of a triangle and its adjacent angle is always ________.