"Tossing a die" is assumed to mean choosing a random face of a cube with faces numbered 1 through 6 such that the probability of choosing any particular face (number) is 1/6.
Event a is "observe a 2". Event b is "observe an even number". The event "a and b" is "observe 2 and an even number". This matches precisely the description for event a. In other words
... a and b = a
... p(a and b) = p(a) = p(choosing 2) = 1/6