Following pls find my worked solution:
Apply <Unchanged Difference> concept (since both A,J weekly expenditure were same), difference between A, J weekly allowance and A, J weekly savings are same.
i.e. A - J (weekly allowance) = $4 = A - J (weekly savings)
Given difference in savings (A - J) = 80 - 40 = 40,
total number of weeks = 40 ÷ 4 = 10
Weekly Savings (A) = 80 ÷ 10 = 8
Weekly Savings (J) = 40 ÷ 10 = 4
Total Weekly Savings (A + J) = 12
Total Weekly Allowance (A + J) = Total Weekly Savings + Total Weekly Expenditure
= 12 + 56
Trust this helps.
Do let me know again if there's further clarification.