1. The expression $iv + 7u$ represents a linear combination of two variables $i$ and $u$, where $v$ and $7$ are coefficients multiplying $i$ and $u$ respectively. 2. The expression $8w - d$ is a linear expression involving two variables $w$ and $d$, where $8$ is the coefficient of $w$ and $d$ is subtracted from it. 3. The expression $5x + 3y$ is a linear combination of variables $x$ and $y$, with coefficients $5$ and $3$ respectively. 4. The expression $7pq$ represents the product of three factors: the constant $7$ and the variables $p$ and $q$ multiplied together. 5. The expression $5x + 4$ is a linear expression with variable $x$ multiplied by $5$ plus a constant term $4$. Each expression is a combination of variables and constants using addition, subtraction, or multiplication, commonly used in algebra to represent relationships or quantities.