#### Answer

$100$ cards

#### Work Step by Step

Let number of cards be x.
The cost for pristine printing cards would be $15 + 0.1 x$
The cost for printing place cards is $10 + 0.15 x$
Set these two equations equal:
$15 + 0.1x = 10 + 0.15x$
Multiply each side by $100.$
$1500 + 10x = 1000 + 15x$
Subtract $10x$ from each side
$1500 = 1000 + 15x-10x $
$1500 = 1000 + 5x$
Subtract $1000$ from each side to isolate $5x.$
$500 = 5x$
Divide both sides by $5$ to isolate $x.$
$x = 100$