This score can be seen as a ratio. You can think of the semicolon as a comparison symbol. It is equivalent to treating a/b=c/d as A: B = C: D. Because your formula is a little troublesome to input, it is more convenient for me to use this formula instead. Using the property of the ratio a:b=c:d, there is ad=bc after deformation. The sum of two internal items is equal to the sum of two external items. Transform it.