we know that
The minor arc ST is equal to the angle ∠SOT by central angle
∠SOT=∠ROU ------> by vertical angles
In this problem we have
∠ROU=
substitute
∠SOT=
so
minor arc ST=
Find the major arc SRT
we know that
The major arc plus the minor arc is equal to
minor arc ST+major arc RST=
Solve for major arc RST
major arc RST=
therefore
the answer is