From the given table, the positive sign connote deposit while the negative sign connotes withdrawal.
If the account shows a zero balance after 4 weeks, we will take the sum of all deposits and withdrawals for the first four weeks and equate to zero as shown:
[tex]+120+(-100)+50+p=0[/tex]
Open the parenthesis:
[tex]+120-100+50+p=0\\20+50+p=0\\70+p=0[/tex]
Subtract 70 from both sides
[tex]70+p-70=0-70\\p=-70[/tex]
Hence the value of p if the account shows a zero balance after 4 weeks is -70
Learn more on deposits and withdrawals here: https://brainly.com/question/11443019