When we talk about two things happening at the same rate, we mean that the ratios of the quantities in the two situations are equivalent. There is also something specific about the situation that is the same.
For example, do these two paint mixtures make the same shade of orange?
To know if the two ratios describe the same rate, we can write an equivalent ratio for one or both ratios so that one quantity has the same value. Then we can compare the values for the other quantity.
Here is a double number line that represents Kiran's paint mixture. The ratio 9:15 is equivalent to the ratios 3:5 and 6:10.
For 10 teaspoons of yellow paint, Kiran would mix in 6 teaspoons of red paint. This is less red paint than Tyler mixes with 10 teaspoons of yellow paint. The ratios 6:10 and 7:10 are not equivalent, so these two paint mixtures would not be the same shade of orange.