One-Step Equations
x - 12 = -5
x = 7
3x + 5 = 20
x = 5
5x + 3 = 3x + 11
x = 4
Find the mistake and the correct answer.
x + 5 = 3
x = 8
They added 5 instead of subtracting it from both sides. The correct answer is x = -2.
3(2x - 4) + 5 = 6x - 5
No solution
-3.5 + x = 6.5
x = 10
I buy a 7lb bag of dry food and a $24 pack of wet food cans for Rune. I spend $59 total. How much did the dry food cost per pound?
$5 per pound
9x - 7 = 4x + 33
x = 8
Find the mistake and the correct answer.
5x + 4 + 2x = 25
11x = 25
x = 25/11
They combined the constant 4 with the x-terms -- you can't combine unlike terms. The correct answer is x = 3.
8x - 3 = 3x + 62
One solution: x =13
-(7/8)x = 21
x = -24
4(x - 3) + 2x = -30
x = -3
8(y - 1) = 5y + 10
y = 6
Find the mistake and the correct answer.
3(x + 4) = 21
3x + 4 = 21
3x = 17
x = 17/3
They only distributed the 3 to the x but not to the 4. The correct answer is x =3.
4(3x + 2) - 5x = 7x + 8
Infinitely many solutions
A cat shelter is at 3/4 of their capacity. They currently have 9 cats. How many can they have at full capacity?
x = 12
3(2x+1) - 5 = 16
x = 3
3(2x + 4) = 5x + 12
x = 0
Find the mistake and the correct answer.
5x + 8 = 2x -4
5x - 2x = -4 + 8
3x = 4
x = 4/3
When moving the 8 to the other side, they added instead of subtracted. The correct answer is x = -4.
(1/2)(4x + 6) - 2 = 2x - 3
No solution
-(5/6)x = -25
x = 30
x = -7
0.4x + 6 = 0.2x + 14
x = 40
Find the mistake and the correct answer.
-5(2x - 4) = -2x + 4
-10x - 20 = -2x + 4
-8x = 24
x = -3
-5 times -4 should be +20, not -20. The correct answer is x = 2.
12x - 18 = 5x + 87
x = 15