Algebra

 

Seven years ago, Grogg's dad was $9$ times as old as Grogg. Four years ago, Grogg's dad was $6$ times as old as Grogg. How old is Grogg's dad currently?   

 

(D – 7)  =  (9)(G – 7)    ..............—>   D – 7  =  9G – 63     (eq 1)   

(D – 4)  =  (6)(G – 4)    ..............—>   D – 4  =  6G – 24     (eq 2)   

 

subtract (2) from (1)                                – 3  =  3G – 39   

 

                                                                  36  =  3G   

 

                                                            Grogg  =  12    

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