On February 5, the directors declare a 15% stock dividend distributable on February 28 to the February 15 stockholders of record. The stock’s market value is $50 per share on February 5 before the stock dividend. The stock’s market value is $43.60 per share on February 28.

15% of $50 (the day they declared the dividend) will turn out to be 17.2% on February 28, but the percentage (usually they don't declare it as a percentage -- they declare an amount) was decided on the day they declared the dividend.

Dividend = $50.00
Ex Dividend **=$ 43.60
____________________

Difference ****= $6.40. JUST ABOUT RIGHT !!

WHY?? = 15% of $50 = $ 7.50.
It should have gone down to $42.50
BUT it maintained its value and actually rose
$1.10.

You can't actually record this without knowing the number of shares outstanding. I'm assuming the problem has this information?