Употребите Past Simple или Past Progressive:

1)When the telephone (to ring) I (to bake) a cake and (to ask) Mary who (to do) nothing at the moment to answer the call.
2)Why you (not to attend) the lecture on Saturday? Professor Brown (to speak) about UFO and other mysterious objects.

1) When the telephone ( rang) I (was baking) a cake and ( asked) Mary who (was doing) nothing at the moment to answer the call. 2) Why didn't you attend) the lecture on Saturday? Professor Brown (spoke/was speaking) about UFO and other mysterious objects

When the telephone rang I was baking a cake and asking Mary who was doing nothing at the moment to answer the call. Why didn't you attend the lecture on Saturday? Professor Brown was speaking about UFO and other mysterious objects.