Suppose a cellphone company offers a monthly plan for a smartphone that includes 6 gigabytes of data for $100.
Each additional gigabyte (or fraction thereof) costs the user $10.
if Ryan subscribe to this plan, how many gigabytes
of data can he use each month while keeping his total cost to no more than $135 (before taxes)?

Ryan can use at most ___ gigabytes of data each month while keeping his total to no more than $135