Why is the fossil named Ida so important to comparative anatomists?

Fossils are usually named based on the following conditions-

These fossils are again categorized into different groups depending on the similarity in terms of form.

These names of the fossils are important to the comparative anatomists because it helps them in doing the comparative study and understand the causes of similarities and dissimilarities in terms of anatomy and also helps in understanding the evolutionary process of these organisms. For example, the fossil named 'Ida' is the primitive fossil that was found to be almost completely preserved. This fossil helped in comparative studies with other fossil species in a number of ways.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

your spelling is a little off : ]