You can put this solution on YOUR website!
Vicki's age is v so Grace's age is 4v.
Five years ago Vicki's age was v-5 and Grace's age was 4v-5.
At this time there was an age difference of 30 years
(4v-5) -(v-5) = 30
4v - 5 - v + 5 = 30
i.e. Vicki's age is 10 and Grace's age is 40.
5 years ago Vicki was 5 and Grace was 35.
Note : The difference in their ages is always 30 years!