Jessica went shopping at a mall. she bought some dresses that were packed in a shopping bag. the shopping bag was in the shape of a trapezoid. the measure of ∠opm is 10 less than three times the measure of ∠pmn. what is the measure of ∠opm of the shopping bag?

Two angles of the adjacent side of a trapezoid should have a total angle of 180. In You can get this equation: 
∠OPM + ∠PMN= 180
∠OPM = 180- ∠PMN

∠OPM = 3(∠PMN) -10 
 180- ∠PMN= 3∠PMN -10 
 180+10= 3∠PMN + ∠PMN
 4  ∠PMN= 190
 ∠PMN= 47.5

∠OPM + ∠PMN= 180
∠OPM + 47.5= 180
∠OPM = 180-47.5= 132.5