Answer:
80°
Step-by-step explanation:
Plot two lines: line passing through the points R, S and U and line passing through three points V, S and T (see attached diagram).
These line intersect at point S and form four angles: RSV, VSU, UST and TSR.
Angles VSU and RST are vertical angles, angles RSV and UST are vertical angles. Vertical angles are congruent, so
m∠VSU = m∠RST = 100°
m∠RSV = m∠UST
Angles RSV and VSU are supplementary angles (add up to 180°). Som
m∠RSV = 180° - m∠VSU =180° - 100° = 80°
Angle RSV is angle VSR (we can read from the right to the left or from the left to the right angle's name)
