Sharon earns $25 per item. This means that this number is increasing with each item sold, then you will have a variable with this number, such as 'x'.
Plus a base salary of $100 per week. This means that this number is always true for each week and will not change when looking at a weekly perspective.
How many items must she sell to earn at least $700 per week. This is the end goal or even slightly over $700.