• model situations that can be represented by first-degree expressions

Write an expression or equation to represent each situation.

The cost to rent a DVD player is a $25 deposit plus $10 for each day. How much will it cost to rent a DVD player for four days? For 10 days? For d days?

Bruce bought some licorice. It cost $3.75 for the first kilogram and $3.25 for each additional kilogram. How much would he pay for 3 kg? 10 kg? m kg?

Write an expression or equation to solve the following problem. A mail-order record club allows you to buy 10 CDs for $1. You then must buy 10 more at $15 each over the next 12 months. What is the cost per CD if you fulfil your obligation?

Write an expression to represent the following situation. Kim earns $12 per hour and pays 20% income tax. Calculate his net income for a 40-hour week and for a 25-hour week.

There is a relationship between mass and height of a person, such that the average mass of a person in kilograms can be estimated by taking three-quarters of his or her height in centimetres and subtracting 72. Does this work for your mass and height? According to the equation, what should your mass be? What is it? Compare your results with others. Does the rule work?

• write equivalent forms of algebraic expressions, or equations, with integral coefficients

Which of the following expressions is equivalent to 3x - 2 = 4? Justify your choice.

3x = 6     -2 = 12x     x = 2      x = -6

Explain how -5x - 6 = -40, 5x + 6 = 40, and 15x + 18 = 120 are related.