Given the following question:
Data plan A
Monthly fee of 52$
$18 per gigabyte
$70 in total for the monthly fee and the 18 dollar gigabyte
Data plan B
Monthly fee of $32
$22 per gigabyte
$54 in total for the monthly fee and the 22 dollar gigabyte
54 + 22 = 76
We want the two phones to be equal in cost so we have to keep adding both in till we have our answer.
70 + 18 = 88
88 + 18 = 106
...
76 + 22 = 98
98 + 22 = 120
...
106 + 18 = 124
124 + 18 = 142
...
120 + 22 = 142
So for the GB data charge to be the same we need 4, $22 of GB for plan B, and 5, $18 GB of plan A.