南方大厦原名“城外大新公司”，楼高50米12层，是广州首幢钢筋混凝土结构的高层建筑。城外大新公司是20世纪二三十年代广州最著名的购物娱乐场所，其中经营了百货商场“环球货品”、亚洲酒店、觉天酒楼、西堤天台花园等。
南方大厦在1919年落成后，超越了上海有利大楼，成为中国最高的建筑物，该纪录维持至1927年。那是南方大厦的黄金时代，也是广州的黄金时代。
南方大厦的建造时间处于粤海关大楼（1916）和爱群大厦（1937）之间。在空间上，南方大厦大致位于粤海关大楼和爱群大厦之间的黄金分割点上，三个谜宝的虚拟坐标即精确体现了这一几何关系。
如何找到宝藏：这个谜宝的藏宝位置不在其虚拟坐标上，请您在Certitude输入以下算式的结果，即可知道最终位置。
(a/b)(c/d)-(b/c) = ?
The Nanfang Building, originally known as the Sun Company Building upon its construction, stands proudly on the West Bund, once the CBD of Guangzhou. Upon its completion in 1919, the Nanfang Building surpassed the Union Building in Shanghai to claim the title of China's tallest structure. Holding this prestigious record until 1927, its reign coincided with the golden age of Guangzhou.
The Nanfang Building is located roughly at the golden point between the Custom House and the Oi Kwan Hotel, two other iconic landmarks adorning the West Bund. The posted coordinates for their respective mystery caches accurately capture the spatial relationship between these architectural marvels.
However, the final location of this cache is not at the posted coordinates. To unveil its true location, please input the result of the following equation into Certitude.
(a/b)(c/d)-(b/c) = ?
You can validate your puzzle solution with certitude.