Answer:
a = 3, b = 4, c = 5
Explanation:
Assuming we're working with a right triangle, where c is the hypotenuse, then using the definition of the cosine being the adjacent side over the hypotenuse, then we know:
a = 3, because it is the side adjacent to B
b = 4, because it is the side adjacent to A
c = 5, because it is the denominator in bot fractions
This of course assumes that there is no additional ratio in place. For example, if the lengths were instead 8, 6 and 10 respectively, then the cosines given would still be 4/5 and 3/5. Truthfully these only tell relative sizes of the sides, and not their absolute sizes.