Algebra Review problems HELP!?! PLEASE!!?
It's like I just forgot how to do algebra, it's been a year since my last math class. I've tried the problems but I don't get the correct answer.
1. c/7 + 2 = 1
2. 6 - 3a/2= -6
3. 75 + 7x = 2x
4. 3n - 1 = 5n - 9
5. 60c - 54(c - 2) = 0
6. 22d - (6+2d) = 4
7. x - (-4x + 2) = 13
Comments
1. c/7 + 2 = 1
subtract 2 from both sides
c/7 = -1
multiply both sides by 7
c = -7
2. 6 - 3a/2= -6
subtract 6 from both sides
-3a/2 = -12
divide both sides by -3
a/2 = 4
multiply both sides by 2
a = 8
3. 75 + 7x = 2x
subtract 2x from each side
75 + 5x = 0
subtract 75 from both sides
5x = 75
divide both sides by 5
x = 15
4. 3n - 1 = 5n - 9
subtract 3n from both sides and add 9 to both sides
8 = 2n
divide both sides by 2
4 = n
n =4
5. 60c - 54(c - 2) = 0
distribute 54
60c - (54c - 108) = 0
distribute negative sign
60c - 54c + 108 = 0
subtract 54c from 60c
6c + 108 = 0
subtract 108 from both sides, then divide by 6
6c = -108
c = -18
6. 22d - (6+2d) = 4
distribute negative sign
22d - 6 - 2d = 4
add 6 to both sides and subtract 2d from 22d
20d = 10
divide both sides by 20
d = 1/2
7. x - (-4x + 2) = 13
distribute negative sign
x + 4x - 2 = 13
add x and 4x, add 2 to both sides
5x = 15
divide both sides by 5
x = 3
1.
c/7 + 2 = 1 iff (isolate the term with the variable, c/7)
c/7 = -1 iff
c = -7
2.
6 - 3a/2 = -6 iff
-3/2 a = -12 iff (multiply both side by the reciprocal of coefficient, which is -2/3)
a = 8
3.
75 + 7x = 2x iff (move variable to one side, then the number to the other side)
75 + 5x = 0 iff
5x = -75 iff
x = -15
4.
3n - 1 = 5n - 9 iff
-1 = 2n - 9 iff
8 = 2n iff
n = 4
5.
60c - 54(c - 2) = 0 iff (be wary of - sign. be sure to distribute to each term)
60c - 54c + 108 = 0 iff
6c + 108 = 0 iff
6c = -108 iff
c = -18
6.
22d - (6 + 2d) = 4 iff (be way of sign distribution)
22d - 6 - 2d = 4 iff
20d - 6 = 4 iff
20d = 10 iff
d = 1/2
7.
x - (-4x + 2) = 13 iff (be wary of sign!)
x + 4x - 2 = 13 iff
5x - 2 = 13 iff
5x = 15 iff
x = 3
1. c=-7
2. a=8
3. x=-15
4. n=4
5. c=-18
6. d=1/2
7. x=3
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