Question: Point R is on line segment QS. Given RS = 2x - 1, QR = 5x + 3, and QS = 5x + 10, determine the numerical length of QS.
1. **State the problem:** We have a line segment $QS$ with point $R$ between $Q$ and $S$. We know the lengths $RS = 2x - 1$, $QR = 5x + 3$, and the total length $QS = 5x + 10$. We need to find the numerical length of $QS$.
2. **Use the Segment Addition Postulate:** The length of $QS$ is the sum of the lengths $QR$ and $RS$ because $R$ lies between $Q$ and $S$.
$$QS = QR + RS$$
3. **Substitute the given expressions:**
$$5x + 10 = (5x + 3) + (2x - 1)$$
4. **Simplify the right side:**
$$5x + 10 = 5x + 3 + 2x - 1$$
$$5x + 10 = 7x + 2$$
5. **Solve for $x$:**
Subtract $5x$ from both sides:
$$\cancel{5x} + 10 = \cancel{5x} + 7x + 2$$
$$10 = 2x + 2$$
Subtract $2$ from both sides:
$$10 - 2 = 2x + \cancel{2} - \cancel{2}$$
$$8 = 2x$$
Divide both sides by $2$:
$$\frac{8}{\cancel{2}} = \frac{2x}{\cancel{2}}$$
$$4 = x$$
6. **Find the length of $QS$ by substituting $x=4$ into $QS = 5x + 10$:**
$$QS = 5(4) + 10 = 20 + 10 = 30$$
**Final answer:** The length of $QS$ is $30$.