Compare and contrast the solutions of a-3=15 and a-3> 15

In 

a - 3 = 15, a can only be 18

in a - 3 >15, a can be numbers 19+ (19 and above) 
(Note:it cannot be 18, because 18 - 3 = 15, and it is only greater than, not greater than and equal too)

hope this helps

The third box is a function

A’b’c’ are the coordinates to the new location of the transformed triangle abc. find the distance between the coordinates points to use for your calculations.