The sum of the measures of two angles is 180 degrees. one angle measures 3a and the other angle measures 2a-25. find a. then find the measures of each angle

So let being angle A and angle B ,the sum of these angle measures is equal 180 degrees 

m<A +m<B = 180°

suppose angle A measure 3a and angle B measure 2a-25 
this mean that 

3a +2a-25 = 180 
5a = 205

a = 205/5 = 41

so than a=41 than the measure of angle A = 3a = 3*41 = 123 degrees 
and the measure of angle B = 2a-25 = 2*41 -25 = 82-25 = 57 degrees 

123 +57 = 180 

hope helped