To simplify a three-term ratio, divide all terms by their highest common factor.<br><br>
&bull; The HCF of 35, 25, and 15 is 5.<br>
&bull; 35 ÷ 5 = 7<br>
&bull; 25 ÷ 5 = 5<br>
&bull; 15 ÷ 5 = 3<br>
<br>
Final Answer: 7 : 5 : 3