Answer:
They'll have the same amount of money after 90 days.
Explanation:
The amount of money Penny has after "x" days is the sum of the initial amount she had (180) plus the product of the days that passed with how much she gets each day. This can be expressed in the following equation:
Penny = 6*x + 180
The amount of money Nick will have can be expressed in the same way, but he didn't have any money in the beggining so it'll be only the amount he gets each day. We have:
Nick = 8*x
To know the amount of days it'll take for them to have the same amount we need to make the two equations equal. We have:
Penny = Nick
6*x + 180 = 8*x
8*x - 6*x = 180
2*x = 180
x = 180/2 = 90 days
They'll have the same amount of money after 90 days.