Is it possible to plug in the answer choices in a problem that has two equations with two variables? And more specifically, is it possible to plug in the answer choices when each answer choice represents the sum of two variables (i.e. a + b and none of the equations of the problem have the term a + b)?
Plugging in—choosing your own numbers or using the answer choices—is a great tool to have when applicable, but, unfortunately, as you have probably noticed, we can't always use it.
This is one of those problems in which plugging in doesn't really get us anywhere. We just have to set up the two-variable equations and solve.
Now, is it sometimes possible to plug in the answer choices in a problem that has two equations with two variables?
There is an example in this post:
And here a few more posts on plugging in on the GMAT:
- How to Solve Two Equations with Two Variables
- How to Plug in Numbers on GMAT Math Questions
- Always Start with Answer Choice C