Solve the real-world situation by using the substitution method. One smartphone plan costs $30 per month for talk and messaging and $8 per gigabyte of data used each month. A second smartphone plan costs $60 per month for talk and messaging and $3 per gigabyte of data used each month. Let c represent the total cost in dollars and d represent the amount of data used in gigabytes. The system of equations lbrace c = 30 + 8d c = 60 + 3d can be used to represent this situation.

How many gigabytes would have to be used for the plans to cost the same? What would that cost be?

Both plans would cost $
if gigabytes of data are used.