Cosmetic = 20%
Remaining = 80%
To frnds = 40% of 80% of x
Remaining = 60% of 80% of x = Piggy Bank

60% of 80% of x = 20% of x + 40% of 80% of x - 6
.48x = .2x + .32x - 6
.04x = 6
x = 600/4 = 150

To frnd = .32/4 * 150 =. 0.08 * 150 = 12

[spoiler]{A}?[/spoiler]

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Algebra complicates the way out of these kinds of questions; moreover the risk of inane errors is potential too. Percent questions on GMAT are best cracked taking 100 as the base total, because they choose numbers for this little reason only, so that if the right way is adopted, calculations would go real smooth.

If her pocket money is 100, then she must have spent 20 on cosmetics and 40 percent of 80 that's 32 on her four friends such that each of her friend receives 8 (we are to answer what this 8 is equivalent to) from her. In this manner, she spent a total of 20 + 32 = 52 on cosmetics and friends, and saved 100 - 52 = 48 to the piggy bank such that SPENT - SAVED = 52 - 48 = 4 (in question it's given to be $6). Now let's ask if 4 is equivalent 6, then 8 is equivalent to...