Solution: B': (7,4)
As we have a triangle, we move each point according to the statement of exercise. We have B = (1,7). As we have to move right 6, that would be increasing X value. So, we have:
X initial: 1. We move right 6, X final= 1+6; X final=7
We down 3, so that would be decreasing Y value.
Y initial= 7. We move down 3, Y final=7-3; Y final=4
According to that, the new point B' would be= (7,4)