False, An example would be an equilateral triangle with 3 sides of 3 inches, and another with three sides of 5 inches. They will be similar but not congruent because their sides differ. because the sides and volumes differ they will not be congruent.
Im pretty sure that it would be 600%. If it was 600% that would be 600 over 100 which would be 6
These are not similar. For them to be similar, they need to exist in proportion to each other for every single side. The ratio of the 12:9 sides is 4:3 when reduced. The ratio of the other 2 sides is 5:3. They all have to have the same ratio for them to be similar.
The answer to this is x = 2