¿cual es la expresion matematica para dos magnitudes que se relacionan de una forma directamente proporcional?

Acertain substance has a solubility of 12 grams in 100 grams of water at 20°c. this means that when 12 g of the substance are dissolved in 100 grams of water, the solution will be saturated when 12 g of the substance are dissolved in 100 grams of water, the solution will be dilute the substance will begin to dissolve when 12 grams are present in solution when 12 grams of the substance are stirred into a beaker with 100 g of water, it will begin settling at the bottom