My 8th-grade son is working on simplifyi

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My 8th-grade son is working on simplifying algebraic fractions in Algebra 1. On his test today, he had these two problems:
1) Simplify (2x + 8) / 2 -> He wrote: x + 8 (he slashed the 2 in 2x and the 2 in the denominator, leaving +8 untouched).
2) Simplify (3a + 12) / 3 -> He wrote: a + 12

When I asked him about it, he said: "There's a 2 on top and a 2 on the bottom, so they cancel out to 1." He doesn't realize that division distributes across the entire numerator, not just the first term. He is canceling an additive term instead of a common factor.

Could you format this into our mistake notebook using the strict 5-line cause card format:
1. Line 1: 题面 (Problem statement & expressions)
2. Line 2: 错法 (Exact error and student's illegal single-term cancellation)
3. Line 3: 修法 (Factoring out GCF 2(x+4)/2 = x+4 or splitting fraction 2x/2 + 8/2 = x+4)
4. Line 4: tag (Category & topic tags)
5. Line 5: 错因 (The core root cause in one direct sentence)

Please keep strictly to the 5 lines without verbose academic filler, plus 1 parallel test problem to verify retention tomorrow.