Question 1200739
f = father's age
x = his son's age.
f = 5x
f-4 = 9*(x-4)
in the second equation replace f with 5x to get:
5x-4 = 9*(x-4)
simplify to get:
5x-4 = 9x-36
subtract 5x from both sides of the equation and add 36 to both sides of the equation to get:
32 = 4x
solve for x to get:
x = 8
f = 5x means f = 40
f-4 = 36
x-4 = 4
36 = 9 * 4.
solution is confirmed to be good.
solution is father's present age is 40.