I've learned English long time, but I have seen difficult thing for remembering.
At the same tim, with a letter when i 've been read this way, and another time also read another.
First case: ape, ache, explain, /ei/
Second case: at, taxi, anniversary, laboratory /e/
Third case: consonant /er/.
If someone have completly pronounce rules, please post here for every one and me. I'm expecting for your reply