You deposit $50 in your savings account. one week later, you withdraw $20. write each amount as an integer

Depositing means that you added 50$ to your account. This means that you account increased by an amount of 50.
The integer describing this is +50.

Then, withdrawing means that you took money from the account. This means that your account decreased by an amount of 20.
This can be expressed as a -20 integer.

The first one is 2/3the second is 1/160the third is 4/125

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