All quadrilaterals add up to 360o for interior angles. The opposite angle of the 115o angle will also be 115o as this is the rule for parallelograms. Therefore this leaves 130o unaccounted for, as 360-(2*115) = 130
Using the same rule as above, the 2 remaining angles must be equal so 130/2 will give the soluiton for the specified angle.
65o