64 ? 17 ? 2 = 98

1. 64 + 17 = 81
2. 81 + 2 = 83. This does not equal 98. Re-evaluating. 64 - 17 = 47. 47 * 2 = 94. This does not equal 98. Re-evaluating. 64 + 2 = 66. 66 + 17 = 83. Re-evaluating. 17 * 2 = 34. 64 + 34 = 98.