Bill is 88 years old. How old is Colie?

EMPOWERgmatRichC, thank you for your observation. You are absolutely correct. I forgot to mention the equation B=44 and this equation along with the 2 other equations in C and D, would have provided you with 3 distinct equations and 3 variables.

I did the equations mentally and thus missed this subtle aspect of the explanation. I have updated my solution in light of this observation.

As per Kaplan, this is the explanation (see below). I found this to be a helpful response. The trick here is to use one to plug into the other.
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The correct answer is C

We want to determine the age of Colie. We are told that Bill is 88 years old. Since no other information in given in the question stem, let's look at the statements.

Let's call Colie's age c and Dino's age d. Statement (1) says that c - 4 = 2(d + 2). This equation can be rewritten c - 4 = 2d + 4, and then c = 2d + 8. This is a single linear equation with two variables. This equation cannot be solved for the value of either variable. So the value of c cannot be solved for. Statement (1) is insufficient and choices (A) and (D) can be eliminated.

Statement (2) says that 88 = 2(c + d). This is a single linear equation with two variables. This equation cannot be solved for the value of either variable. So the value of c cannot be solved for. Statement (2) is insufficient as well and choice (B) can be eliminated.

Taking the statements together we have the equations c = 2d + 8 and 88 = 2(c + d). We have two different linear equations in the variables c and d. These two equations can be solved for the values of each variable. Thus, c has a single value that can be solved for. The two statements taken together are sufficient and choice (C) is correct.
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