Explanation

"At" is used for specific places.

Here, "at their home" is the correct preposition.

Explanation

Given:

(x + 5) : (x + 7) = 5 : 7

We can write it as:

(x + 5) / (x + 7) = 5/7

Cross-multiplying:

7(x + 5) = 5(x + 7)

7x + 35 = 5x + 35

7x - 5x = 35 - 35

2x = 0

x = 0

Explanation

Combined rate = 1/6; first pipe rate = 1/10.

Second pipe rate = 1/6 - 1/10 = 1/15.

So, the second pipe alone fills in 15 hours.

Explanation

Total parts = 2 + 3 + 5 = 10

Salma's share = (2/10) × 2000 = 400.

Explanation

Total pages = 10 + 12 + 8 + 10 = 40.

Average = 40 ÷ 4 = 10 pages per day.

Explanation

"Ours" is the possessive pronoun showing ownership of the room.

It refers to "our room" without repeating the noun.

Explanation

"Under" is used to show position below something.

Here, the old man is positioned below the tree, so "under" fits correctly.

Explanation

Below is used to indicate a lower position than sea level.

Example: The lake is 900 feet below sea level.

Explanation

Mandela led the struggle against racial segregation (apartheid) in South Africa.

He became the country's first Black president in 1994.

Explanation

The Moon is Earth's natural satellite, orbiting our planet.

It reflects sunlight but does not produce its own light like a star.