In (x,y) it represents horizontal, then vertical coordinates. So, if x is 0, that means it hasn't moved left or right. Since y is -7, that means it when down by 7 units from the origin.
You can use the CPCTC (Corresponding Parts of Congruent Triangles are Congruent) property. This means that when two triangles are congruent, all the corresponding parts are congruent to each other.
