Check each option by dividing all three terms by the same factor to see if it matches 1:2:3.<br><br>
&bull; 2:4:6 ÷ 2 = 1:2:3 → equivalent ✓<br>
&bull; 3:6:9 ÷ 3 = 1:2:3 → equivalent ✓<br>
&bull; 4:8:12 ÷ 4 = 1:2:3 → equivalent ✓<br>
&bull; 5:10:25: 5×1=5 ✓, 5×2=10 ✓, but 5×3=15 &ne; 25 → NOT equivalent &cross;<br><br>
Final Answer: 5:10:25