Hi Angel,
3 weeks is really just dipping your toes in, so I wouldn't feel like your current score truly reflects your ability. You can absolutely raise your Quant score in 9 weeks, but it will take a lot of hard work, especially if it's been a long time since you've studied Math.
For DS, the actual questions are distilled into two types: "yes/no" and "value." For "yes/no" questions, you only need enough information that will allow you to conclusively answer either yes or no. There is no "correct" answer. Our task is merely to determine when we have enough information.
For "value" questions, consider what information would be necessary to solve the problem. What pieces of information are missing? For example, to draw a line on a graph we might be missing information such as the y-intercept, the slope, or two points on the line.
Once you determine the type of question and have analyzed the information given, analyze the first two statements independently of each other. Try to "forget" statement 1 before you move on to statement 2. Don't underestimate how challenging this can be!
Write out A through E on your scratch paper as you practice, and use the process of elimination to narrow down choices.
If 1 is sufficient, eliminate B, C, and E. The only two options are A and D.
Conversely if 1 is NOT sufficient, eliminate A and D.
Simply by appropriately analyzing the first statement, you can eliminate two or three answer choices! If statement 1 is challenging for you, you can start by analyzing statement 2. If statement 2 is insufficient, then choices B and D can immediately be eliminated. It doesn't matter which statement you analyze first, as long as you start by looking at them individually.
If neither statement is sufficient on its own, then the options left are C and E. Try combining the statements to see if together they would provide enough information to arrive at an answer. If they don't the answer is E.
Let's look at an example question:
Is c > 2 if a + b + c > 0 ?
(1) c > a + b + 2
(2) a + b + 2 < 0
This is a "yes/no" question. The question is asking if c is greater than 2. First let's analyze the given information before looking at the answer choices. We are told that a + b + c > 0. If we isolate c, that gives us c > -(a + b). To answer this question, we need to determine the values of a and b.
If (a + b) = -2,
c > - (-2)
c > 2
Then the answer would be "yes." What about if (a + b) was smaller or larger than -2?
If (a + b) = -1
c > - (-1)
c > 1
The answer would be "maybe" since there are numbers larger than 1 but smaller than 2.
What about if (a + b) was smaller than -2?
If (a + b) = -3
c > - (-3)
c > 3
The answer would be "yes" since all values greater than 3 are also greater than 2.
So we have determined that we need (a + b) to be a number less than -2. Let's express that as an inequality.
a + b < -2
Now we can evaluate the statements. Statement 2 is equivalent to our inequality and is therefore sufficient. Notice how much work we did before reading the statements!
