Describe the different ways you can compare two similar objects or quantities with equivalent ratios

Well, you could make the ratio so that it's in the form one to something (I.e. 1:n) if you did this to both then you would be able to compare the values. To do this you would have to decide which part you will make one, and divide each side by this number. For example if you had that £50 will buy you 100 tins of paint, you can write this as 100:50. Then to find how much one tin would cost you divide each side by 100. This would give you 1:0.5 so one tin is 50p.
This is the only way I know of that will let you compare values (you can also do the same thing but make the value something other than 1, as long as they are equal).