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

If one of the angles of a triangle is $130^{\circ},$ then the angle between the bisectors of the other two angles can be (in $^{\circ}$)

Prove that a triangle must have at least two acute angles.

Side $QR$ of $\Delta PQR$ is extended on both the sides so that exterior angles $\angle PQS$ and $\angle PRT$ are formed. If $\angle PQS = 100^{\circ}$ and $\angle PRT = 130^{\circ}$,find the measure of each angle of $\Delta PQR$.

In $\Delta ABC$,$\angle A : \angle B : \angle C = 5 : 7 : 8$. Find the measure of each angle of $\Delta ABC$.

In the given figure,if $PQ \parallel RS$,$YZ \perp RS$ and $\angle SZX = 143^{\circ}$,then find $\angle PXZ$,$\angle XZY$ and $\angle YXZ$.