Gwynn and Alison were two sisters who lived in an upscale neighborhood near the best mall in California. The whole Equality family spent a good deal of their time keeping track of everyone's possessions, who owned this or who was buying this car, or that house, or what the kids were going to get for Christmas or how many days it was until someone's birthday. So it was that whenever Gwynn got anything, whether at the mall or for a special holiday, Alison was interested in getting exactly the same thing. In fact both sistersmade a point of keeping track of all the privileges and possessions the other gotso that she could insist on the same.

Now Gwynn was really in a good mood because her uncle had sent her fifty dollars and although she had spent a good deal of this already she managed to "borrow" another twenty from her father's wallet; now she had bought some Louie Voullton sunglasses for 34 dollars. Every Christmas and birthday her uncle gave her money!!!! With no kids he had tremendous disposable income! 
 
 

Naturally Alison, on seeing the new goods her sister had, persuaded Mom to give her an advance on her next birthday. She bought a pair of very expensive sandals with her advance. This made her feel better. 

At this point the girls thought they were at the same level. They were in good moods and lent each other clothes.

Here is how the problem happened. One time Dad went on a business trip to Australia and when he was at the airport at Australia he bought Gwynn some presents. You can see what they were. For Alison he bought two cheap teddy bears. Naturally Alison was furious and wanted a big present so she had the same as her sister.

	Gwynn				Alison
$20	$20	$50		$?	$15

	Gwynn				Alison
$20	$20	$50
$50	$20	$15		$?	$15	$15

Do you think you can solve some problems like this? Think "x" instead of and go to linear equations, first set.