Find the value of $m$ and $n$, where $AB=OB$ and $n=2 \mathrm{m}$.

 

Find the value of $\angle ABC$, if $AC=AB$.

Three lines $AB, CD$ and $EF$ meet at a point $O$, forming angles as shown in the figure. Find the values of $x, y, z$ and $u$.

Find the value of $\angle GFA, \angle CDB$ and $\angle ABE$.

Find the value of $\angle TRS, \angle TRU$ and $\angle PRQ$.

Find the value of $x, y$ and $z$.

Find the value of $\angle DBC$.