# A.2.1.1 Opener - A Main Dish and Some Side Dishes

Here are some letters and what they represent. All costs are in dollars.

*m*represents the cost of a main dish.*n*represents the number of side dishes.*s*represents the cost of a side dish.*t*represents the total cost of a meal.

*m*= 7.50 b.

*m*= s + 7.50 c.

*ns*= 6 d.

*m + ns = t*

Here are some questions to think about: What is an equation? What does it tell us?

Can equations contain only numbers?

Could this equation be true: *m* + 5 = *t*? How do you know?

When might the equation *m* + 5 = *t *be false?

One equation tells us that a main dish is $7.50. Another equation tells us that it is equal to the expression s + 7.50. Could both be true? Are they both appropriate for expressing the cost of a main dish?