$\begin{align}  & R\overset{\wedge }{\mathop{T}}\,S={{90}^{\circ }}\text{   (angle in a semicircle}{{\text{)}}_{{}}} \\ & R\overset{\wedge }{\mathop{S}}\,T={{180}^{\circ }}-({{90}^{\circ }}+{{25}^{\circ }})\text{  (sum of }\angle \text{s in a }\Delta \text{)} \\ & R\overset{\wedge }{\mathop{S}}\,T={{65}^{\circ }} \\ & x=R\overset{\wedge }{\mathop{S}}\,T={{65}^{\circ }}\text{      (alternate segment)} \\\end{align}$