It is not possible to provide an accurate answer with the information provided. There are different masses of two different substances being dissolved in the same amount of water at the different temperature. The solubility of neither solute x nor solute z is known.

Depending on the solubility of the two substances, 100 ml of water may be able to dissolve the 17 g of solute x while 26 g of solute z may not dissolve in the water if the solubility of x is more than z or even if it lesser as a smaller amount of solute x is being dissolved. On the other hand if the solubility of solute z is more than that of solute x, the 26 g of solute z may dissolve in water while 17 g of solute x does not. Unless the solubility of the two substances is known nothing can be inferred.