Question 1147928
Let {{{ x }}} = Xavier's age when they go married
{{{ x + 4 }}} = Yifei's age when they got married
( this is true because the difference in their ages never changes )
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{{{ x + 37 }}} = Xavier's age now
{{{ x + 4 + 37 }}} = Yifei's age now
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{{{ x + 37 + x + 41 = 120 }}}
{{{ x + 78 = 120 }}}
{{{ x = 42 }}}
and
{{{ x + 4 = 46 }}}
Yifei was 46 when they were married