1. 2. 3. 7 = 5 1 4 = 3 6 8 + = X 2 = 9 – – 9 = 3 5 7 = 2 8 1 + = X 4 = 6 – – 5 = 6 8 4 = 1 2 7 + = – 3 = – + – 3 3. 4. + 1 1 1 4. + 1 1 1 4. + 1 1 1 8 = 3 5 7 = 1 2 4 + = – 3 = – + – 6 8 8 8 8 8 8 8 8 8 8 8