Answer:
18 is the old value and 12 is the new value. In this case we have a negative change (decrease) of -33.33333333 percent because the new value is smaller than the old value.
We need the exponents law

So if
a=3
b=1/2
then

where x represent every half a year.
First one costs $720, second costs $700 so the second one the<span> 1,000 dollar computer discounted to 30%</span>
So, the fraction of races that he won was:

: you need ti divide the number of occurrences by the number of possibilities.
We can simplify this:

.
When we write it in decimals until the closest place, it's:
0.167 or 16.667%