SC- QUICK HELP???

Comparison Markers

Below explanation is from Manhattan SC book :
There are different ways to write a logically parallel comparison. For example:
Right: Frank, LIKE his brother, has a broad and muscular build.

This comparison has the structure X, like Y. A similar marker might be Like X,Y. The word like is the most common comparison marker. Here’s another version:
Right: Frank’s build, LIKE that of his brother, is broad and muscular.

A comparison can also use a pronoun to stand in for the noun first mentioned; in the example above, the pronoun that refers to build. This is often considered preferable to repeating the same word—and it allows the GMAT to make the sentence a bit harder.

Some comparison structures can even omit the second main word of the comparison. In the example below, the two parallel structures Frank’s and brother’s imply that the same word follows both: Frank’s build and brother’s build:
Right: Frank’s build, LIKE his brother’s, is broad and muscular.

First one is correct.

Second one uses (what's called as) double possessive. So, second one is basically saying:

Frank's build, LIKE that (build) of his brother's (build), is broad and muscular.

Notice that the second one says: "...(build) of his brother's (build)...".

This is clearly non-sensical. So we can either say:

i) Frank's build, LIKE his brother's,....

Or

ii) Frank's build, LIKE that of his brother,....

p.s. Our book EducationAisle Sentence Correction Nirvana discusses double possessives. Have attached the corresponding section of the book, for your reference.

Hi yaygmat, You may try EducationAisle Sentence Correction Nirvana or Gmat club grammar book for sc.

Have suggested Manhattan-Prep's 6th Edition for SC (and CR) too. Consider checking them out if you feel your fundamentals are a bit slippery. There's also a downloadable idiom list for SC on the GMAT Knight blog you may find helpful.