A: Subtract $5$ from both sides: $2x = 12$. Divide by $2$: $x = 6$.

A: Subject: The students. Predicate: finished the assignment.

A: $F = m \times a$ (force equals mass times acceleration).

A: $H_{2}O$: two hydrogen atoms bonded to one oxygen atom.

A: The mitochondrion, because it produces ATP through cellular respiration.

A: The value of the next best alternative foregone when a choice is made.

A: The Statement of Financial Position (Balance Sheet) and the Income Statement (Profit and Loss).

A: The central idea, message, or insight about life that the author conveys.

A: The tilt of Earth's axis $\approx 23.5^{0}$ as it orbits the sun causes varying sunlight angles and day lengths.

A: A system of government where power is exercised by the people, often through elected representatives.

A: A step-by-step procedure or set of rules for solving a problem or performing a task.

A: Price and quantity in a market are determined by how much sellers supply and how much buyers demand; when demand exceeds supply, prices tend to rise, and vice versa.