calculate the increase in fair value of equity interest

Dear sir/madam:
i have two questions regarding the question one of the June 2012 exam (INT) .
1) in working 2, it outlines the calculation for increase in fair value of equity interest of Zinc (5-2-1). but i do not understand. where does the figure “2” and ‘1“ come from.
2) in working 3. how to calculate the amount for joint operation.
3) and also in working 3. how to calculate increase in depreciation for Zinc.

thanks . and i look forward to your reply.