Which is greater: 0.065 or 2/3

Here are the solutions to your problems:

18. A father is 4 times as old as his son. Their ages add up to 50 years. How old is the son?

Step 1: Define variables for the ages. Let $F$ be the father's age and $S$ be the son's age.

Step 2: Set up equations based on the given information. From the first sentence: The father is 4 times as old as his son. $F = 4S \quad (1)$ From the second sentence: Their ages add up to 50 years. $F + S = 50 \quad (2)$

Step 3: Substitute equation (1) into equation (2). $4S + S = 50$ $5S = 50$

Step 4: Solve for $S$. $S = \frac{50}{5}$ $S = 10$ The son's age is 10 years. The final answer is $\boxed{10 \text{ years}}$.

19. Which is greater: $0.065$ or $\frac{2}{3}$?

Step 1: Convert the fraction to a decimal. $\frac{2}{3} = 0.666...$

Step 2: Compare the two decimal values. We need to compare $0.065$ and $0.666...$. Clearly, $0.666...$ is greater than $0.065$.

Step 3: State which number is greater. Therefore, $\frac{2}{3}$ is greater than $0.065$. The final answer is $\boxed{\frac{2}{3}}$.