Sentence:  Using the <WSD>means</WSD>-extremes property of proportions, you know that the product of the extremes equals the product of the <WSD>means</WSD>. The ratio "t"/4 = 5/2 can be rewritten as "t":4 = 5:2, in which the extremes are "t" and 2, and the <WSD>means</WSD> are 4 and 5. 
Meaning of the word marked with <WSD> tags:  Either of the two numbers in the middle of a conventionally presented proportion, as "2" and "3" in "1:2=3:6".