Let's break down the problem step by step.

Given:

1. On Day 7:

   • The share price of Company A is $4.60.
   • Joyce's mother sells all her shares of Company A and buys 2000 shares of Company B.
   • She receives $7400 after buying the shares of Company B.

2. On Day 12:

   • The share price of Company A is $4.80.
   • The share price of Company B is $0.50 less than that on Day 7.
   • She sells all her shares of Company A and buys 5000 shares of Company B.
   • She has to pay $5800.

We need to find:

1. The number of shares of Company A Joyce's mother has on Day 7.
2. The share price of Company B on Day 12.

Step 1: Find the Share Price of Company B on Day 7

Let the share price of Company B on Day 7 be $P_B$.

When she buys 2000 shares of Company B on Day 7, she uses the money obtained from selling her shares of Company A. So: $\text{Total money from selling shares of Company A} - 2000 \times P_B = 7400$ $\text{Total money from selling shares of Company A} = 2000 \times P_B + 7400$

Step 2: