(8) Increase: \( \begin{array}{llllll}\text { (1) } 40 \text { by } 20 \% & \text { (2) } 45 \text { by } 33 \frac{1}{3} \% & \text { (3) } & \text { R } 50 \text { by } 50 \% & \text { (4) } 2 \frac{1}{2} \text { by } 150 \% \\ \text { (3) Decrease: } \\ \begin{array}{lllll}\text { (1) } 30 \text { by } 10 \% & \text { (2) } 35 \text { by } 20 \% & \text { (3) } 120 \text { by } 25 \% & \text { (4) } 1 \frac{5}{6} \text { by } 40 \%\end{array}\end{array} \)

To increase a number by a percent, multiply the original number by the percent (in decimal form) and then add it to the original number. For example, to increase 40 by 20%, you'd calculate \( 40 \times 0.20 = 8 \), and then \( 40 + 8 = 48 \). Similarly, for the other numbers, just follow the same steps! For decreasing, it's a similar principle but subtract instead. To decrease 30 by 10%, you'd calculate \( 30 \times 0.10 = 3 \), and then subtract: \( 30 - 3 = 27 \). Just remember, increasing adds to your value, while decreasing takes away!