Question 1133879
Let {{{ x }}} = my age
Let {{{ y }}} = my daughter's age
{{{ x = 2y + 20 }}}
subtract {{{ 20 }}} from both sides
{{{ x - 20 = 2y }}}
Divide both sides by {{{ 2 }}}
{{{ y = (1/2)*x - 10 }}}
In words, this is saying that my daughter's age 
is ten years less than half my age
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check:
Suppose I am 40, or {{{ x = 40 }}}, then
{{{ 40 = 2y + 20 }}}
{{{ 20 = 2y }}}
{{{ y = 10 }}}
and
{{{ y = (1/2)*x - 10 }}}
{{{ y = (1/2)*40 - 10 }}}
{{{ y = 20 - 10 }}}
{{{ y = 10 }}}
OK