Pls i need stuck on this question

braelyn is writing an equation to represent the perimeter of a rectangle with the width equal to half the length. she knows that the perimeter is equal to 18 units and needs to find the length and width of the rectangle. which equations represent this relationship? check all that apply.

1. x+0.5x1/2x=18
2. 2x+x=18
3. 2x+2(2x)=18
4. x+0.5x+x+0.5x=18
5. 2(x+0.5x)=18
6. 2x+0.5x=18

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.