Can a triangle have all angles less than $60^{\circ}$? Give reason for your answer.

Ray $BD$ is the bisector of $\angle ABC$ and ray $BE$ is the bisector of $\angle DBC$. If $\angle EBC = 19^{\circ},$ then find $\angle DBC, \angle ABC$ and $\angle ABE$.

If one angle of a triangle is equal to the sum of the other two angles,then the triangle is

The sum of the three angles of a triangle is $\ldots \ldots \ldots$ (in $^o$)

In the given figure,$AB \parallel DE$ and $BC \parallel EF$. Prove that $\angle ABC = \angle DEF$.

In the figure,$\angle 1 = 60^{\circ}$ and $\angle 6 = 120^{\circ}$. Show that the lines $m$ and $n$ are parallel.