Jenny brought in a total of 40 + 50 = 90 cookies.
Marcus brought in a total of 30 + 20 = 50 cookies.
The probability that Renee will have an allergic reaction depends on the number of peanut butter cookies out of the total number of cookies.
Out of the 90 cookies that Jenny brought in, 40 of them are peanut butter cookies.
Out of the 50 cookies that Marcus brought in, 30 of them are peanut butter cookies.
So, out of a total of 90 + 50 = 140 cookies, there are 40 + 30 = 70 peanut butter cookies.
The probability that Renee randomly chooses a peanut butter cookie is therefore 70/140 = 1/2.
To express this as a percentage, we multiply by 100: 1/2 * 100 = 50%.
#### 50
The answer is: 50
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If Jenny brought in 40 peanut butter cookies and 50 chocolate chip cookies, and Marcus brought in 30 peanut butter cookies and 20 lemon cookies, what is the probability, expressed as a percentage, that Renee, who is allergic to peanuts, will have an allergic reaction if she randomly chooses a cookie from the bake sale?

### Answer:
