Question 1062081
"It is .12 cent for each card..."
That is  0.12 CENT per CARD, price being a fraction of a cent.  As a dollars price, 0.0012 DOLLARS per CARD.


The base price of $15 is for "no cards yet printed", so if you are using x for how many cards and y for the cost, then b is for the base price; and you can use y=mx+b.  Fill in the data to express {{{y=0.0012x+15}}}.


How many cards were printed, given that {{{y=45}}}?  This is the same as, "solve for x, if y=45".
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{{{y-15=0.0012x}}}
{{{(y-15)/0.0012=x}}}
{{{x=(45-15)/0.0012}}}
{{{x=30/0.0012}}}
{{{highlight(x=25000)}}}