15. Convert the following values into scientific notation. \( \begin{array}{ll}\text { a) } 42,670,000 \div 42 \cdot 67 \times 10^{4} \\ \text { b) } 0.0000008\end{array} \)

Multiply. Simplify. \( 25 \times 1 / 10 \)

Find the absolute value of \( 5 \).

3. List all the pairs of whole numbers that multiply together to create the product 200 . \( 2 \times 100 \quad 8 \times 25 \) \( 4 \times 50 \quad 20 \times 10 \)

Consider the following arithmetic sequence. \[ \begin{array}{l} 2, \frac{9}{2}, 7, \ldots \\ d=\square \\ a_{1}=\square \\ \text { (a) Identify } d \text { and } a_{1} \\ \text { (b) Write the next three terms. } \\ a_{4}=\square \\ a_{5}=\square \\ a_{6}=\square\end{array} \]

Multiply. Simplify. \( 8 \times 1 / 5= \)