randRange(1, 9)
randRange(2, 9)
10 * A_10 + A_1
randRange(0, A_10 - 1)
randRange(0, A_1 - 1)
10 * B_10 + B_1
0
graph.subtractor = new Subtractor( A, B );
graph.subtractor.show();
NUM_HINTS = graph.subtractor.getNumHints();
A - B
graph.subtractor.showHint();