设在一定温度下,将某硝酸钾溶液100g含有硝酸钾固体 x 克.

(x-2.5)/(100-60-2.5) = (x-7.5)/(100 - 80 -7.5)
==>(x-2.5)/37.5 = (x-7.5)/12.5
==>37.5 * (x - 7.5) = 12.5 * (x - 2.5)
==>3(x-7.5) = (x-2.5)
==>3x - 22.5 = x - 2.5
==>2x = 20
==>x =10
另设在该温度下,硝酸钾的溶解度是 y.
y/(100+y) = (10-7.5)/(100-80-7.5)
==>y/(100+y)= 2.5/12.5
==>5y = 100 + y
==>4y = 100
==>y = 25
在该温度下,硝酸钾的溶解度是 25 克.