No it is undefined when the number reaches to zero.
Since 4 nights cost $356, 356÷4=89, so one night costs $89. 7-4=3, so 89×3 is 267. 267+356 is 623. The total cost for 7 nights would be $623
Okay so i would do this with a logarithm.
5^(2x) = 28
take the log of both sides
log5^(2x) = log28 and because of this log rule: logA^n = nlogA
(2x)log5= log28
then divide by log5 on both sides
2x = log28 / log5
and divide by 2
x = (log28 / log5) /2
this can be found with a calculator:
x= about 1.03521...
round that to whatever the question says to