How to find angles, with explanation please

Question

AOB and COD are straight lines, find <a, <b and <c

Answer 1

If a straight line meets another straight line, the sum of the two adjacent angles so formed is equal to two right angles.

b = 25^O

Angle on straight line is 180 ^O.

a + b =180

a + 25=180

a = 155^O

Angle on straight line is 180 ^O.

90 + c + 25 =180

c + 115 =180

c= 65^O