Answer:

Step-by-step explanation:
Let P% of the transaction amount is charged in the account.
So, if the transaction amount is x, then the charge for that transaction will be
.
Therefore, if f(x) represents the amount Isabel is charged for the transaction then we can write
, where P% is the rate of charge. ( Answer )
Answer:
Step-by-step explanation:
He paid $107 for the sneakers (55+55)*0.7 = 107.
He paid $30 for socks, so in total he paid $137