Father A is twice the age of the difference in years of the ages of
Father B and Son A, who is one and a half times older than Son B.
Father B is currently twice the age of Son A is going to be when Son B will be double the age he is now.
All of the ages are multiples of five.
How old is Father A?
The respective ages (in years) of Son A, Father A, Son B and Father B are 15, 70, 10 and 50.