Concept:Form a pair of linear equations from the given age conditions and solve for the present ages.Explanation:Let the present ages of mother and son be M years and S years respectively.One year ago, mother’s age was M−1 and son’s age was S−1.Given: M−1=5(S−1)So, M=5S−4 …(1)After 6 years, mother’s age will be M+6 and son’s age will be S+6.Given: M+6=2(S+6)+5Substitute M=5S−4 into this equation:(5S−4)+6=2(S+6)+55S+2=2S+12+55S+2=2S+173S=15S=5Now substitute S=5 into equation (1):M=5(5)−4=21Therefore, the present ratio of mother’s age to son’s age is:M:S=21:5Answer:21:5​, which is option D.