Answer:
<em>She would need to make 5 consecutive free successful throws</em>
Step-by-step explanation:
<u>Equations</u>
A basketball player wants to improve his percent of successful throws to 85%.
She currently has made 12 out of 15 free throws, which gives a success percentage of 12/15*100=80%
So, she needs a number of free consecutive free throws to increase that number to the desired target.
The percentage of success can be calculated as:

Let's assume x is the number of required consecutive successful throws. Since she has already thrown 15 times, out of which has had 12 successful throws, now she will have 15+x total throws and 12+x successes, thus the new percentage is:

And this percentage must be equal to 85%, thus:

a) The equation to represent the situation is:

b) Let's solve it.
Multiply by 15+x:

Dividing by 5:

Operating:

Subtracting 17x and 240:

Simplifying:

Dividing by 3:
x = 5
She would need to make 5 consecutive free successful throws