30 + 25 = 55;
30 − 25 = 5;
42 + 25 = 67;
42 − 25 = 17;
67 + 25 = 92;
67 − 25 = 42;
50 + 25 = 75;
50 − 25 = 25;
25 + 25 = 50;
25 − 25 = 0;
49 + 25 = 74;
49 − 25 = 24.