Answer:
10.5
Explanation:
Tanisha's regular recipe uses 3p of potatoes for making a quantity X.
So, we could say thay using 3p of potato she gets X salad. In an equation, and assuming there is a proportional relationship between the pounds used and the salad got:
3 = X
Now, if she wants 3.5 more salad, it is, 3.5X salad, she will also need 3.5 more potatos:
3 * 3.5 = 3.5 X
10.5 = 3.5 X
So, Tanisha needs to buy 10.5 pounds of potatoes