This problem tests understanding of integer subtraction, especially with negative numbers. On the number line, #3 is already below zero. Subtracting 7 means moving seven more units to the left. Starting at #3 and moving left seven spaces results in #10. Another way to think about this is to rewrite the problem as adding a negative number: #3 # 7 is the same as #3 + (#7). When adding two negative numbers, you add their absolute values and keep the negative sign. The absolute values of #3 and #7 are 3 and 7, and 3 + 7 = 10, so the result is #10. Option A is therefore correct. Option B is a common mistake when students subtract absolute values incorrectly. Options C and D are positive and would only occur if the signs were misunderstood. The NEX Math Section frequently includes integer operations to assess number sense and sign awareness.