Note that in this equation, the number 54.1 is a constant: it isn't multiplied by anything. So 54.1 is a minimum number: a femur cannot have a minimum length, so even if  were to equal zero, the estimated height would be 54.1. This tells you that 54.1 has to be the absolute minimum estimated height of a hominid using this method.

Since we know that  stands for weeks, the answer has to have something to do with the weeks. This eliminates "the number of candles she has remaining for the month." Also, we can eliminate "the number of weeks that she has sold candles this month" because that would be our value for , not what we'd multiply  by. The correct answer is,  "the number of candles that she sells each week."

When you see formulas like this that express the total cost for a number of items, there are some standard components you should recognize. Whenever there is a plain number added, with no variable next to it (as you see with + 10 here), that is a fixed charge that does not depend on the number of items purchased.  Where you do see a number multiplied by a variable, like with 12s here, that represents the amount of money that depends on the number of items purchased: the numerical coefficient is the cost-per-item, and the variable is the number of items. Which should make logical sense - the shopper gets to choose the number of items to buy, so that number can vary customer to customer, making a "variable" appropriate there. Here you're asked about the number 12, which is multiplied by the variable s - that means that 12 is the price per shirt, with s being the number of shirts Shawn purchases.

In this equation you know that  is the total number of pizzas and that  is the number of football games. Think about what happens: if  increases, there are more pizzas ordered.  tells us how many extra pizzas are ordered for each game that is being televised. The pizzeria would sell 10 pizzas if no games were on TV, 13 if one is on, 16 if two is on, etc.  So  is the number of additional pizzas expected to be ordered per football game on TV.

An exponential change calculation generally has three components: the initial amount, the percent change, and the number of periods that have undergone that change. The typical structure of such a calculation is:

New Amount = Original Amount(1 +/- Percent Change As A Decimal^{)Number of Periods}

Here we're dealing with a 12.8% decrease, so within the parentheses the percentage is subtracted, and  has been identified as the number of periods.  is the original amount that gets multiplied by the percent change taken to its exponent, so the correct answer is the original amount, which in this problem is defined as "The number of square kilometers of ice in Greenland as of September 30, 1979." 

In this problem, Sarah's income is quoted as an annual amount but her expenses are quoted as a monthly amount. In order to calculate her savings, she needs those units to both be in either "per year" or "per month." Since the variable  also represents a number of months, it is necessary for her to convert her annual salary into a monthly amount so that she can properly subtract expenses from income to reflect the amount of money saved. Therefore, dividing by 12 is how she makes that conversion.