In this seed you will spawn close the tree. To find the combined dungeon you need cross over that tree about 10-15 blocks, turn around see a tree which is in the ground. Dig straight down from here and after a while you will fall down to the combined dungeon and mineshaft. In mineshaft have lot of interesting things, but the answer will be your.
Seeds : 1405000953 Work in PE ver0.10.0+ or ver0.10.5