Raul used the steps shown below to solve the equation. In which step did Raul make a mistake? \[ \begin{array}{l}5 x-3(2 x+7)=2 x+9 \\ \text { Step 1: } 5 x-6 x-21=2 x+9 \\ \text { Step 2: } \quad-11 x-21=2 x+9 \\ \text { Step 3: } \quad-13 x=30 \\ \text { Step 4: }\end{array} \]

\( | \frac { 2 x - 1 } { x + 1 } - 2 | < \varepsilon \)

10. Matador Wireless offers a data plan that charges \( \$ 10.00 \) a month for access, with no additional charge if usage is at or below 75 MB . If a customer exceeds 75 MB of data they are also charged 10 cents for each MB above 75 . If a customer exceeds 125 MB of data, they are charged 40 cents for each MB above 125 . a. What is the monthly cost to store 125 MB of data? b. Write a formula for the piecewise function of the cost function for storing \( x \mathrm{MB} \) of data a month. Fill in the boxes for the piecewise definition for the cost \( C(x) \) of storing \( x \) MB of data a month. \[ C(x)=\left\{\begin{array}{cc}10 & \text { if } 0 \leq x \leq 75 \\ 10+0.10(x-75) & \text { if } 75<x \leq 125 \\ 10+0.10(50)+0.40(x-125) & \text { if } x>125\end{array}\right. \]

Solve the equation. If necessary, round to the nearest thousandth. \( 7^{x+3}=6^{x} \) A. \( \{37.87\} \) B. \( \{-39.33\} \) C. \( \{-37.87\} \) D. \( \{-36.41\} \)

Find the range of the quadratic function, \[ y=-3 x^{2}-12 x-15 \] Write your answer as an inequality using \( x \) or \( y \) as appropriate, Or, you may instead click on "Empty set" or "All reals" as the answer, प<ロ \( \square>\square \)

Simplify. \[ \frac{10 y^{2}-25 y}{5 y^{2}-15 y} \]