Question 1108160
I will say that he had $100 to spend
That means each granola bar costs {{{ 100/90 }}} dollars
and each pop tart costs {{{ 100/78 }}} dollars
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I can say:
{{{ ( 100/90 )*75 + ( 100/78 )* x = 100 }}}
Divide both sides by {{{ 100 }}}
{{{ 75/90 + x/78 = 1 }}}
{{{ x/78 = 90/90 - 75/90 }}}
{{{ x/78 = 15/90 }}}
{{{ x/78 = 1/6 }}}
{{{ x = 78/6 }}}
{{{ x = 13 }}}
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check:
{{{ 75/90 + 13/78 = 1 }}}
{{{ 5/6 + 1/6 = 1 }}}
OK