Grandpa age is 6 years less then 6 time juniors age the sum of their age is 78 find the each of their age

Grandpa is 6 years less than 6 times junior’s age. Let’s translate that in math form.
6 times juniors age(j) minus 6
6j - 6

The sum of their games is 78. Add Junior’s age with Grandpa’s.
6j-6 +j = 78.

Now add like terms and solve for j.
7j-6 = 78
+6 +6

7j= 84
———-
7
j= 12

Junior is 12 years old.

Substitute j to Grandpa’s equation.

6(12) - 6
72 -6
66

Grandpa is 66 years old.