Jinfa, upon receiving his paycheck, spent four-fifths of it on car repairs and then bought a $40 gift for his mother. He had $64 left. How much was his paycheck?

You’ll do it in reverse here so
$64 + $40 = $104
if he spent 4/5 on car repairs then had a remaining $104, the 1/5 is equal to $104.
multiply $104 by 5 and it gives you $520

his paycheck was $520

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