Answers:
minor arc RP = 125 degrees
minor arc QS = 125 degrees
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Explanation
Definition: A minor arc is a piece of a circle such that it is smaller than a semi-circle with the same radius. In other words, it's measure is always less than 180 degrees.
Based on this definition, a minor arc is where we take the shortest path between any two points on a circle. For minor arc RP, we start at R then go to the right and take the shortest path to P. We do not go left when we start at R because that's the longer path and it is the major arc.
Minor arc RP is subtended by central angle ROP = 120 degrees. This central angle is equal to the arc measure in question. This isn't really a theorem, but more a definition if anything.
Central angle QOS is equal to angle ROP through the vertical angles theorem. Any pair of vertical angles are always congruent. Since QOS is 125 degrees, so is minor arc QS.