the average age of three people running for election is 42. a fourth person joins the race and the average…

Explanation:

Step1: Find sum of first three ages

The formula for the average $\bar{x}=\frac{\sum_{i = 1}^{n}x_{i}}{n}$. For $n = 3$ and $\bar{x}=42$, the sum of the ages of the three - person, $S_1$ is $S_1=42\times3 = 126$.

Step2: Find sum of four ages

For $n = 4$ and $\bar{x}=40$, the sum of the ages of the four - person, $S_2$ is $S_2=40\times4=160$.

Step3: Find the fourth person's age

Let the age of the fourth person be $x$. We know that $S_2=S_1 + x$. So $x=S_2 - S_1$. Substitute $S_1 = 126$ and $S_2 = 160$ into the equation, we get $x=160 - 126=34$.

Answer:

B. 34