Point A is located at (0,2). It moves to A ' (0,6). Focus on the y coordinates. We go from y = 2 to y = 6. This is a jump of multiplying by 3. We have multiplied every coordinate of A by 3 to get corresponding coordinates for A'.
Point B will be treated the same way. It starts off at B = (2,3) and moves to B ' = (6,9) after multiplying both coordinates by the same scale factor 3.