what is the best approach to the cost compare

If one bottle costs more than one cap, which statement is true?

1. one bottle + one cap costs more than two bottles
2. one bottle costs more than two caps
3. two caps cost more than one bottle
4. one bottle + one cap costs more than two caps
5. two bottles cost more than three caps

how to solve questions like this? what should be the approach?

You could solve it by rewriting the expressions into inequalities and graphing it out.

Making inequalities

For how to graph it, check this link

So I would basically see this as a set of inequalities, substituting caps with x and bottles with y

One bottle costs more than one cap, then becomes y > x

one bottle + one cap costs more than two bottles, becomes y + x > y + y and then rewrite this to y < x

one bottle costs more than two caps, becomes y > 2*x

and so on.

Plotting it out

Then plot the two inequalities into a coordinate system, like shown here

For the first question you'll see that no values satifies both y > x and y < x