Answer:
4.2 gigabytes
Explanation:
To find the answer, you need to write an equation where the cost of Carolina Cell is equal to the cost of Sanford Cell:
20.79+2x=22.89+1.50x, where x is the number of gigabytes used.
Now, you can solve for x:
2x+1.50x=22.89-20.79
0.5x=2.1
x=2.1/0.5
x=4.2
According to this, the answer is that both plans would cost the same when 4.2 gigabytes are used.