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! =)
Welp, what IIIIIIIIIII like to do is SOLVE the problem FIRST, THEN see what steps we did and convert it to an equation. ;-)
So FIRST; IF the gum was 3 cents less than what the pack costed BEFORE, we would have to ADD 75 + 3 = 78, THEN divide 78 by 3 to get 26, so the pack of gum costed 26 cents 20 years ago. We had to divide because we had to do the opposite operation than what the problem started with to reverse and find the original price of the gum. You could test it by doing 26 times 3, - 3 which equals 75.
NOW, We could replace the original cost of the gum by "x" in this problem. C. would be the correct choice since it EXACTLY replicas what we did above; Multpily x, (26), by 3 to get 78, then subtract 3 to get 75. I hope I helped! =D
