Exercise 21 Page 354

To find the two numbers, first we need to write each phrase as an equation. Let's call the first number $a$ and the second number $b.$ The phrase $\text{three}$ times a number $\text{minus}$ another number is $\text{-}3$ can be written algebraically by equating $\text{-}3$ with the $\text{difference}$ of $\text{three}$ times $a$ and $b.$ The second phrase, the $\text{sum}$ of two numbers is $11,$ can be written algebraically by equating $11$ with the $\text{sum}$ of $a$ and $b.$ Combining these equations, we get a system of equations. Since $b$ and $\text{-}b$ have opposite coefficients, we will solve this system using the Elimination Method by addition. The two numbers are $2$ and $9.$