Let x be the number of transactions made on ATM for each plan.
We know that their local plan charges $13 monthly and $6 for any transaction beyond six, then its cost is:
![3(x-6)+13](https://img.qammunity.org/2023/formulas/mathematics/college/j26stbecsxk0g8rs1azoaho0hmtckhl20g.png)
Now, anywhere plan charges $19 monthly plus 1.75 for every transaction then its cost is:
![1.75x+19](https://img.qammunity.org/2023/formulas/mathematics/college/zrvynzdb0vw78g9gy78lw7nt62pzngrx4x.png)
Now we want to know for how many transactions anywhere plan cost less, then we have:
![\begin{gathered} 1.75x+19<3(x-6)+13 \\ 1.75x+19<3x-18+13 \\ 19+18-13<3x-1.75x \\ 24<1.25x \\ x>(24)/(1.25) \\ x>19.2 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/w8o4q8vu5ntobohpay8n3j6xsliro33w1u.png)
Therefore Anywhere plan will cost less for 20 or more transactions.
(we round up since we can't have a a decimal amount of transaction)