Children learn by using their senses and to adjust their cognitive schemes.
3 - x = 2^2
3 - x = 4
-x = 4 - 3
-x = 1
x = -1
I would say an investigation is a part-by-part scrutiny of a given problem. An investigation is examining a problem as to for example, what happened, how did it happen, when and why and re the consequences.
The answer to 1/5 ^-2
is C=25