Twenty-one students at a school have an allergy to peanuts, shellfish, or both.
 fourteen students at the school are allergic to peanuts.
 twelve students at the school are allergic to shellfish.
how many of the students are allergic to both peanuts and shellfish?
a 12
b 7
c 5
d 2

step-by-step explanation:

if you want to solve percent error follow these steps.

1. subtract the accepted value from the experimental value.

2. take the absolute value of step 1.

3. divide that answer by the accepted value.

4. multiply that answer by 100 and add the % symbol to express the answer as a percentage.

if you want to solve percent of change just do this.

1. work out the difference (increase) between the two numbers you are comparing.

2. divide the increase by the original number and multiply the answer by 100. if your answer is a negative number then this is a percentage decrease.

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step-by-step explanation: