A. 3
Step-by-step explanation:
Because we know that the angles of this triangle are 30-60-90, we know that we can find the length of the sides. Because all 30-60-90 triangles follow the proportions for the sides that are shown in the picture, we can use that to find the length.
The side we are looking for is the side opposite the 60° angle, which is on the bottom, or the long leg. We have the measure for the short leg provided, which is 3, shown in the photo as x. The long leg that we are looking for is equal to ()x. We know x is 3, so we can plug it in. ()3 = 3