Hello Francisca,
In 46.2 you could solve the exercise 2 ways:
If sales increase by 10%, Contribution Margin will also increase by 10%, going from 108 000€ to 118 800€ (I didn't really understand where you got the 15 000€ from.)
Then, fixed costs would increase from 120 000€ to 135 000€ (15 000€ is the monthly cost from the promotional campaign). Therefore profit would be -16 200€
The other way would be to use the concept of Operating Leverage. 108 000€ / -12 000€ = -9, this is, if profits increase by 10%, losses will decrease by 90%. Initial losses would go from -12 000€ to -1 200€, but then you would have to add the 15 000€ of fixed costs from the promotional campaign, getting to a profit of -16 200€
In 46.3 the exercise says that the company will remove products that were being sold at their variable costs, which were 50% of sales. Therefore sales decrease by 50%, which is 180 000€. On top of these, remaining sales decrease by 20%, meaning, from 180 000€ to 144 000€. Variable costs will initially decrease by the same amount, 180 000€, because you are removing products that were being sold at their cost. Afterwards, the remaining variable costs also decrease by 20% due to the same decrease in sales, going from 72 000€ to 57 600€. Then you just need to remove 15% of fixed costs.
Hope this helps!