Since this is a right triangle, we can use one of the three main trigonometric functions: sine, cosine, or tangent.
Remember: SOH-CAH-TOA
Looking from the angle, we know the opposite side and want to know the adjacent side. Therefore, we should use the tangent function.
tan(61) = 47 / BC
BC = 47 / tan(61)
BC = 26.05 units
Hope this helps!