The vertical angle of an isosceles triangle is $100°$. Find its base angles.
 

In a $△ABC$, if $3\angle A=4\angle B=6\angle C$, calculate the angles.

In the figure, the value of $x$ equals :

In a right triangle $ABC, AD=AE$ and $CF=CE$ as shown. If $\mathrm{\angle }DEF=x$ degrees then the value of $x$ equals

In the diagram if $△\mathrm{A}\mathrm{B}\mathrm{C}$ and $△\mathrm{P}\mathrm{Q}\mathrm{R}$ are equilateral. The $\angle \mathrm{C}\mathrm{X}\mathrm{Y}$ equals

In Figure, line AB $\parallel$ line CD and line PQ is the transversal. Ray PT and ray QT are bisectors of $\angle BPQ$ and $\angle PQD$ respectively.

Prove that $\angle PTQ=90°$