Question 228894
Dan is 1/6 his father's age.
d = {{{1/6}}}f
or
f = 6d
: 
In 4 years, Dan will be 1/4 his fathers age.
d + 4 = {{{1/4}}}(f+4)
: 
what is Dan's age?
:
Replace f with 6d in the last equation
d + 4 = {{{1/4}}}(6d + 4)
Multiply both sides by 4
4(d + 4) = 6d + 4
:
4d + 16 = 6d + 4
:
16 - 4 = 6d - 4d
:
12 = 2d
:
d = 6 yrs is Dan's age
;
:
Check solution:
f = 6(6) = 36
"In 4 years, Dan will be 1/4 his fathers age." 
6 + 4 = 1/4 * 36 + 4