100
A student records the mass of a lump of clay, x. Next, a second lump of clay, y, is added to lump x, and the combined (x+y) 90 grams of mass are recorded. Finally, a third lump of clay, z, is added to the combined (x+y+z) mixture, and the final (x+y+z) mass are recorded as 190 grams, as shown below.
What is the most heavy lump of clay?
Lump Z