Question 201940
Let {{{x}}} = my age now
given:
Other person'a age is {{{40}}}

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Assume the other person is older, in
other words, I am younger than {{{40}}}
I will always be (other person's age) - (difference in our ages)
The difference in the ages is always {{{40 - x}}}
{{{40 = 4*(x -(40 - x))}}}
{{{40 = 4*(x - 40 + x)}}}
{{{40 = 4*(2x - 40)}}}
{{{40 = 8x - 160}}}
{{{8x = 200}}}
{{{x = 25}}}
I am 25 years old
check answer:
when the other person was my age, I was
{{{40 - 25 = 15}}}
and
{{{40 = 4*(x -(40 - x))}}}
{{{40 = 4*(25 - 15)}}}
{{{40 = 40}}}
OK