Explanation:
To see whether ratios are equivalent you would try to simplify them by multiplying the number and denominator by the same number in way that they don’t become decimals.
6:4 can be divided by 2 to make its simplest form of 3:2. However 18:8 can also be divided creating its simplest from of 9:4. Since 9:4 and 3:2 aren’t the same they aren’t equivalent ratios.