IAR Grades 6-8 Ratios and Proportional Relationships. Practice it free.

$6.60 \times 6 = 39.6$.

Multiply across: $\dfrac{3 \times 3}{6 \times 7} = \dfrac{9}{42} = \dfrac{3}{14}$.

The constants $15$ and $-7$ are like terms: $15 - 7 = 8$. The term $r^{2}$ stays the same, so the expression is equivalent to $r^{2} + 8\textsf{.}$

Distribute 5: $5 \cdot 9x + 5 \cdot -5 = 45x - 25$.

Use a conversion factor with pounds in the numerator so ounces cancel: $112 \text{ oz} \times \dfrac{1 \text{ lb}}{16 \text{ oz}} = 7 \text{ lb}$.

$3^{4} = 3 \cdot 3 \cdot 3 \cdot 3 = 81\textsf{.}$

The base $6$ appears $3$ times as a factor, so $6 \times 6 \times 6 = 6^{3}$.

Multiply by 100: $0.36 \times 100 = 36\%$.