She has 6 left.
70%= 0.7
0.7 x 20 = how many she has sold (14)
OR
30%=0.3
0.3 x 20= how many she hasn't sold (6)
<span>A perfect power is a positive integer that can be expressed as an integer power of another positive integer.
More formally, n is a perfect power if there exist natural numbers m > 1, and k > 1 such that

.
Sometimes, some fractional or decimal radicants are not perfect power, yet they evaluate to a terminating decimal or recalling decimal.
Example: 6.25 is not a perfect power, but

.
Therefore, </span><span>A radical whose radicand is not a perfect power is a rational number</span> SOMETIMES.