Question 938722
gal + mother + dad = 100
x Dad's age
{{{(x-5)/2 + (x-5) + x = 100}}} |Multiplying thru by 2 so as all denominators = 1
(x-5) + 2(x-5) + 2x = 200
(x-5) + 2x -10 + 2x = 200
5x = 215
x = 43, Dad's age, mother 38 {{{43-5}}}  and gal 19 {{{38/2}}}
And...checking
sum = 100