Question 1192048
let x = the age of his youngest child.
then 55 = 2 * x + 5.
that's your equation.
solve for x to get:
x = (55 - 5) / 2 = 50 / 2 = 25.
his son's age is 25.
he is twice that plus 5 = 55.
the general equation is y = 2 * x + 5.
if you know his son's age, then you solve for y.
if you know his age, then you solve for x.