So, to find how to simplify this, you need to: 1) Find a number that can be divided by <u>BOTH </u>21 and 28. 2) Divide <u>BOTH</u> 21 and 28 by that number.
Let's do it! <u>7</u> is the number that can be divided by BOTH 21 and 28; 21 ÷ 7 = 3 28 ÷ 7 = 4 So, the answer is: 3:4
<em>I hope this helps! If it did, a Brainliest would be really appreciated! <3 </em>Have a great day!