There are 108 tiles and 9 lights what is the ratio of lights to tiles

The ratio is 1:12 ...

The ratio of tiles to lights is 108 to 9, which we can write as 108:9

This ratio has any number of equivalent ratios which you find by multiplying or dividing * both * numbers by the same multiplier. You could double this to find the equivalent ratio of 216:18. You could divide both by 9 to find the equivalent ratio of 12:1 - this one is called a unit ratio because it the number of tiles per 1 light.