Afair coin is tossed 4 times. what is the probability it will land tails up each time?

Considering you have a 50/50 chance on each flip, you'd have so many combinations of what it could do.
H = Heads
T = Tails

= 4 heads
HHHT = 3 heads | 1 tail or 3 tails | 1 head
HHTT = 2 heads | 2 tails
= 4 tails.

Considering the immense amount of combinations, the answer would be:

1/16 chance because you have 4 different combinations of possibilities in the coinflip.