Four Variables for Mac

From Polymath Love Software:

Four Variables is a pre-algebra investigation for students in grades five through nine. The program secretly assigns values to four variables (w, x, y, and z) and the student must find these values by requesting the computer to perform operations with the variables. For example: the student might ask the program to divide x by z; the program would respond "x/z = 0.875." The are two different investigation types: one where all four operations are allowed, and one where only division is allowed.