When rounding a number, the digit of the number can be increased up to 1, but the digit won't be decreased. So, it is possible to round a five digit number into six digit number. But to increase the number digit, the number should be rounded up. To be rounded up, a number should have value 5 or more.
The correct answer is: -2(5+4n)
Kevin will water both of his plants on the 15th.
The lowest common multiple of 3 and 5 is 15. Therefore, he will water both then.