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The answer is 150 parents. Because 450/3=150
x = number of 1-cent stamps
y = number of 8-cent stamps
z = number of 12-cent stamps
We have 31 stamps all together, so x+y+z = 31.
"I have 4 more 1-cent stamps than 8-cent stamps" means we have the equation x = y+8. Whatever y is, add 8 to it to get x. Solve for y to get y = x-8.
You also have "twice as many one cent stamps as 12 cent stamps", so x = 2z. Solving for z gets you z = 0.5x
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x+y+z = 31
x+x-8+z = 31 ... y replaced with x-8
x+x-8+0.5x = 31 ... plug in z = 0.5x
2.5x-8 = 31
2.5x = 31+8
2.5x = 39
x = 39/2.5
x = 15.6
Your teacher made a typo somewhere because we should get a positive whole number result for x (since x is a count of how many 1-cent stamps we have).
80 = -1(80), -2(40), -4(20), -5(4),
Total answers include: -81, 79, -42, 16, -9, and 1.
None of them add up to 6!
Are you doing polynomial equations?
If so, you can solve it the hard way.
x^2 + 6x -80 = 0
(x^2 + 6x + 9) - 80 = 9
(x+3)^2 = 89
(x+3) = 9.43
x = 6.43
If you're not doing those then I'm afraid your question has no answer.
Hope that helps!
