Question

Help me pleaseee I really need help

Answer 1

`\boxed{\text{A. 110 jazz, 440 rock}}`

Explanation:

Let r = the number of rock CDs

and j = the number of jazz CDs

You have a system of two equations:

`\begin{cases}(1) & r = 4j\\(2) & r + j = 550\end{cases}\\\begin{array}{lrcll} & 4j + j & = & 550 &\text{Substitited (1) into (2)}\\& 5j & = & 550 &\text{Combined like terms}\\(3) & j & = & 110 &\text{Divided each side by 5}\\& r & = & 4 * 110 &\text{Substituted (3) into (1)} \\& r& = & 440 & \text{Substituted (5) into (1)}\\\end{array}\\\text{There are $\boxed{\textbf{\110 jazz, 440 rock}}$ CDs}\\`

Check:

`\begin{array}{rclcrcl}440 & = & 4 * 110 & \qquad &440 + 110&=&550\\440 & = & 440 & \qquad &550& = &550\\\end{array}`

OK.