Question 1055439
Let {{{ x }}} = the number in the numerator
The unknown fraction is:
{{{ x / ( x + 2 ) }}}
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Add {{{ 1 }}} to both numerator and denominator
{{{ ( x + 1 ) / ( x + 2 + 1 ) = 4/5 }}}
{{{ ( x + 1 ) / ( x + 3 ) = 4/5 }}}
Multiply both sides by {{{ 5*( x + 3 ) }}}
{{{ 5*( x + 1 ) = 4*( x + 3 ) }}}
{{{ 5x + 5 = 4x + 12 }}}
{{{ x = 7 }}}
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{{{ x / ( x + 2 ) = 7 / ( 7 + 2 ) }}}
{{{ x / ( x + 2 ) = 7 / 9 }}}
The fraction is 7/9
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check:
{{{ ( x + 1 ) / ( x + 3 ) = 4/5 }}}
{{{ ( 7 + 1 ) / ( 7 + 3 ) = 4/5 }}}
{{{ 8/10 = 4/5 }}}
{{{ 4/5 = 4/5 }}}
OK