6x2, because using pemdas, 2x2= 4 then 4x3=12. The answer must equal 12, and 6x2 does.
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Answer:
7.
Step-by-step explanation:
21 = 3 * 7
28 = 2 * 2 * 7
42 = 2 * 3 * 7
Collecting common factors:
t is common to all 3 sets of factors so
HCF = 7.
