This problem should be resolved by trial and error.
1st scenario.
Husband is 50 years old and Wife is 91 - 50 = 41 years old
When husband was 41 years old , she was 41 - 9 = 32 years old Ratio : 41/ 32 = 1,28
2nd scenario
Husband is 55 years old and Wife is 91 - 55 = 36 years old
When husband was 36 years old, she was 36 - (55-36) = 17 years old Ratio : 36/ 17 = 2.11
3rd scenario
Husband is 54 years old and Wife is 91 - 54 = 37 years old
When husband was 37 years old , she was 37- (54-37) = 20 Ratio ; 37/20 = 1,85
Age of husband is between 54 - 55 , and wife between 36 - 37
Solution
Husband is 54,6 years old and wife is 36,4 years old
When husband is 36,4 years ols, she was 36,4 - (54,6 - 36,4 ) = 18,2 Ratio = 36,4/18,2 = 2