Confusing stuff! giving out 50 big points!

a pack of gum costs 75 cents. that is 3 cents less than three times what the pack cost 20 years ago. which equation could be used to find the cost of the gum 20 years ago?

a) 0.3x - 0.3 = 0.75
b) 0.03x - 0.3 = 0.75
c) 3x - 3 = 75
d) 3 - 3x = 75

leave an explanation for your answer so i can understand. you! : d

If the gum costs 75 cents today, which is 3 cents less than three times what the pack cost 20 years ago, we just need to arrange what we know into an equation.
We know that the price of gum today is 75 cents, so we can leave that on one side of the equation as a constant. Also, since we are dealing only with cents and not dollars, there is no need to shift the decimal point to the left.

? = 75

Now, we can work the equation.

The problem tells us that 75 is 3 cents less than three times the old cost. So, if x is the old cost, we can work out the equation based on that.
It says that it's 3 cents less than 3 times x. The question is basically the equation in word form.

3x - 3 = 75

'3x' being the "three times the old cost" part, '- 3' being the "3 cents less" part, and '75' of course being the current price of a pack of gum.
Option C is your correct answer.

BTW if we were to solve this, we would see that the old price of a pack of gum is:

3x - 3 = 75
   + 3      + 3

3x = 78
/3      /3

x = 26

20 years ago, a 75-cent pack of gum cost 26 cents.
Hope that helped! =)