Choose the student who correctly used substitution to determine if 19 was a solution to the equation. Mara's work Juan's work Acacia's work Hector's work​

How many real and imaginary solutions does the equation x^2-3x=-2x-7 have?

If i have one apple and give you the apple, how many apples do i have?

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.