Let me rephrase this for you
5.00-1.97=?
$1.97 + ______ = $5.00?
Subtract $1.97 from $5.00 and you'll find your answer.
$1.97 + x = $5.00
$5.00 = $1.97 + x
$5.00 - $1.97 = x
$3.03 = x
$1.97 + $3.03 = $5.00