Answer:
Part A: Angle R is not a right angle.
Part B; Angle GRT' is a right angle.
Step-by-step explanation:
Part A:
From the given figure it is noticed that the vertices of the triangle are G(-6,5), R(-3,1) and T(2,6).
Slope formula

The product of slopes of two perpendicular lines is -1.
Slope of GR is

Slope of RT is

Product of slopes of GR and RT is

Therefore lines GR and RT are not perpendicular to each other and angle R is not a right angle.
Part B:
If vertex T translated by rule

Then the coordinates of T' are


Slope of RT' is

Product of slopes of GR and RT' is

Since the product of slopes is -1, therefore the lines GR and RT' are perpendicular to each other and angle GRT' is a right angle.