Answer:
P = 499.2 Watt
Step-by-step explanation:

3/7
6 divided by 2 equals 3
14 divided by 2 equals 7
$72 - $30 = $42
It increased $42.
Now take this number and divide by the original number (first):
42 ÷ 30
This is 1.4, let's convert this to a percentage.
We now times it by 100
1.4 × 100
The answer is 140%
18x
Simple as that. 18 times however many times she cuts the grass