The normal systolic blood pressure P, in millimeters of mercury, for an adult male x years old can be modeled by the equation `P=(x+220)/2`. According to the model, for every increase of 1 year in age, by how many millimeters of mercury will the normal systolic blood pressure for an adult male increase?

Explanation

To solve the problem, we need to determine how the normal systolic blood pressure \( P \) changes with an increase in age \( x \) by 1 year. The given equation for blood pressure is:

\[ P = \frac{x + 220}{2} \]

### Step 1: Define the blood pressure for the current age
Let \( P_1 \) be the blood pressure for an adult male who is currently \( x \) years old. Using the equation, we can express it as:

\[ P_1 = \frac{x + 220}{2} \]

### Step 2: Define the blood pressure for the next age
Now, let \( P_2 \) be the blood pressure for the same adult male when he is \( x + 1 \) years old. We can express this as:

\[ P_2 = \frac{(x + 1) + 220}{2} \]

### Step 3: Simplify \( P_2 \)
We can simplify \( P_2 \):

\[ P_2 = \frac{x + 1 + 220}{2} = \frac{x + 221}{2} \]

### Step 4: Calculate the increase in blood pressure
To find the increase in blood pressure when the age increases by 1 year, we calculate the difference \( P_2 - P_1 \):

\[ P_2 - P_1 = \frac{x + 221}{2} - \frac{x + 220}{2} \]

### Step 5: Combine the fractions
Since both terms have the same denominator, we can combine them:

\[ P_2 - P_1 = \frac{(x + 221) - (x + 220)}{2} \]

### Step 6: Simplify the numerator
Now, simplify the numerator:

\[ P_2 - P_1 = \frac{x + 221 - x - 220}{2} = \frac{1}{2} \]

### Conclusion
Thus, the increase in normal systolic blood pressure for an adult male for every increase of 1 year in age is:

\[ \frac{1}{2} \text{ mmHg} \text{ or } 0.5 \text{ mmHg} \]