Something here is not right. A triangle has a total of 180 degrees. Given A and B, the 3rd angle C = 35o. Maybe you mean c = 15; the length of side c, which is opposite angle C. Then the law of sines gives:
a/sin 45 = 15/sin 35
a = 15 sin 45/sin 35
= 15 X 1.2328
= 18.492, approx
