Answer: (Looking back, I may have gotten this question wrong, but if I haven't then nice.)
a) 13 degrees
b) acute angle
Explanation:
Given that we know a triangle is 180 degrees. Lets recall what an obtuse, acute, right and reflex angle are.
Obtuse: An angle greater than 90 degrees
Acute: An angle less than 90 degrees
Right: An angle that is 90 degrees
Reflex: An angle in between 180-360 degrees
Since we know that two of the three angles are 54 and 113 degrees, we can say that 54+113+x=180. That means that the missing angle, x, is 13 degrees.
Knowing that 13 is less than 90, we can also say that the third angle is an acute angle.