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Patty because she has the lowest time out of them all. From least to greatest Patty would be the least with her time being shorter than the rest
3a + a - 15 = 225 . your substituting b(a-15) into the first equation. <span />
Scientific notation implies that all the zeros are taken away and replaced with a 10 raised to whatever appropriate power would be necessary to make the number in scientific notation equal to the original number.
In the number 780,000,000, we can see that there are 7 zeros, but the number before the zeros has two digits, so we need to tuck the decimal point in there, because the number has to be between 1 and 10 for math reasons.
7.8 ... but what do we raise it to? We know it has to be 10, but to what power? Well, we just count how many places to the left the decimal point has traveled. From the original number, the decimal point shifted 8 places to the left, so that is the number that we will raise the 10 to.
The final number looks like this:

780,000,000 in scientific notation is <span>

Hope that helped =)</span>