Concepts are ones that we know by a specific set of characteristics that are always exhibited

Artificial

Explanation:

When we do not observe or understand any concept directly from our subjective experience, it is an artificial concept. Therefore, there are a specific set of exhibited characteristics which are not natural — for example, defining various basic shapes such as geometric shapes. Square has a particular set of attributes of four equal sides, for instance. Again, a triangle has three sides and three angles. The artificial concept can expand the knowledge by giving the original meaning of something before proceeding to the formulas.

x=3

step-by-step explanation:

this is really simple i saw that there was only one term (5x) and thought if that was 15 what would i have to multiply everything else to get it there? well if 5x became 15 then x would have to be 3 so plug the 3 in the x for the other equations and you get 15 for the other ones. so there you go. : )