Steps
So here are a couple expressions when a value changes by percentage (p = percentage in decimal form and m = original value):
- When decrease: (1 - p)m
- When increase: (1 + p)m
So firstly, the $80 share dropped by 15%. Since this is a decrease, follow the appropriate expression:

On Tuesday, the share went from $80 to $68
Next, on Wednesday the share increased by $7. With this, just add $68 and 7.

On Wednesday, the share went from $68 to $75
Lastly, on Thursday the share increased by 12%. Since this is an increase, follow the appropriate expression:

Answer
The final price of the share is $84.