Solve for x. this is very confusing

What properties allow transformation to be used as a problem solving tool

The table below shows the approximate height of an object x seconds after the object was dropped. the function h(x)= -16x^2 +100 models the data in the table. for which value of x would this model make it the least sense to use? a. -2.75 b. 0.25 c. 1.75 d. 2.25

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9