By the interior angles theorem, if angle a is 25 degrees and angle b is greater than 51 degrees but less than 57 degrees what are the possible measurements for angle c

I guess you are talking about a triangle . The 3 angles add up to 180 degrees.

b +  c = 180 - 25 = 155 degrees

When   b  > 51 degrees  then

c  <= 155 - 52

c <= 103 degrees

When b < 57

c >= 155 - 56

c >= 99 degrees

Possible measurements  for angle c :=

99   =<  c  <= 103  (answer).

all it means is function 3