Answer:
She increased 80% the practise time
Explanation:
The question is incomplete, the following is missing:
by how much did she increase the time she practised each day?
From Monday to Wednesday she increased 90 - 50 = 40 minutes the practise time.
To compute the increment as a percentage use: increment/reference *100
In this case, that is: 40/50*100 = 80%, where 50 minutes is taken as a reference.