The sum of the present ages of the father and son is 80 years. When the father’s age was equal to the present age of the son, the sum of their ages was 40 years. What are their present ages?
F==Father, S==Son, D==Difference between their ages
F + S ==80.............. (1)
F - S ==D................ (2)
S+(S-D)=40...............(3), solve for F, S, D
Use substitution or elimination to get
F ==50 years - father's age
S ==30 years - Son's age
D ==20 years - difference between their ages.
