In this question, we are given that the average age of Raj and his father is 45 years. Let`s assume Raj`s age as x years. Since the father`s age is 2 times that of Raj, the father`s age would be 2x years. The sum of their ages is then x + 2x = 3x.

We are also given that the grandfather`s age is 3 times that of Raj`s age, so the grandfather`s age would be 3x years.

To find the average age, we need to divide the sum of their ages (3x) by the number of people (2), which gives us 3x/2.

According to the given information, the average age of Raj and his father is 45 years. So, we can set up the equation 3x/2 = 45.

Solving this equation, we find x = 30.

Since we need to find the age of Raj`s grandfather, we substitute x = 30 into the expression for the grandfather`s age: 3x = 3 * 30 = 90.

Therefore, the age of Raj`s grandfather is 90 years.