hey Vera,

*Explanation*:

2 coins were put everyday. The coins could either be a 20-cent or 50-cent or both then. In other words, it can be two 20-cent coins, two 50-cent coins or one 20-cent and one 50-cent coins. Hope this is useful.

Following pls find my worked solution:

(a)

182 ÷ 7 = 26

182 × 2 = 364

364 + 26 = **390**

(b)

26 $1 coins were were put into box. Hence, value = $26.

Amt left: 13390 - 2600 = 10790

Number of coins (20-cent & 50-cent) = 364

Use <Assumption> method,

Assume all 364 coins are 50cents, total value = 364 × 50 = 18200

D1: 18200 - 10790 = 7410

D2: 50 - 20 = 30

D1 ÷ D2 = 7410 ÷ 30 = 247 (number of 20-cent coins)

Hence, number of 50-cent coins = 364 - 247 = **117**

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Trust this helps.

Do let me know again if this is different from your Answerkey or if theres further clarification.

Cheers

Edward