1. **Problem statement:** Find the gradient of the straight line joining points A and B. 2. **Formula for gradient:** The gradient $m$ of a line joining points $A(x_1,y_1)$ and $B(x_2,y_2)$ is given by: $$m=\frac{y_2 - y_1}{x_2 - x_1}$$ 3. **Important rules:** - The gradient represents the "rise" over the "run" (vertical change over horizontal change). - Positive gradient means the line slopes upwards from left to right. - Negative gradient means the line slopes downwards from left to right. - Parallel lines have the same gradient. 4. **Given points:** $A(1,3)$ and $B(2,6)$. 5. **Calculate the gradient:** $$m=\frac{6 - 3}{2 - 1} = \frac{3}{1}$$ 6. **Simplify:** $$m=3$$ 7. **Interpretation:** The gradient of the line joining points A and B is 3, meaning the line rises 3 units vertically for every 1 unit it moves horizontally. **Final answer:** $$\boxed{3}$$