Subtraction equations - Homework help
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Subtraction equations - Homework help

[From: ] [author: ] [Date: 11-08-15] [Hit: ]
x=22! This method is more on a 6-8th Grade level.......
I need assistance in showing my son how to solve the following subtraction equations. I know that you are supposed to isolate the variable on one side. How would i do i solve the following problems. Thank you

18 - x = 4 (i know the answer is 14)
11= 15 - b ( i know the answer is 4)

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when you are getting started write all of the steps out remember you want all the x's on one side and everything else on the other

18 - x = 4 so subtract 18 from both sides
18-18 - x = 4 -18
-x =-14 divide by -1
-x / -1 = - 14/-1
x= 14

11= 15 - b
11-15 = 15 - 15 -b
-4 = - b
b=4

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okay for the first one do the opposite of x. so subtract 18 on both sides since you're trying to solve for x. then divide both sides by -1 since -x is multiplied by -1 in the first place. the main concept is to get x by itself. second one you have to subtract 15 on both sides and then divide by -1 on both sides. always remember that whatever variable you're trying to solve for do the opposite of whats being done with the variable.

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If "you are supposed to isolate the variable on one side", try using inverse operations! For example, for 18-x=4, do the opposite of the math function, in this case subtraction, addition with the number on the left side and do this on the number on the right side.

x=4
x=|+18
x=|----------
x=|22

and.... x=22! This method is more on a 6-8th Grade level.

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18 - x = 4
18 - x + x = 4 + x add x to each side
18 = 4 + x the x's on the left side cancel
18 - 4 = 4 + x - 4 subtract 4 from each side
14 = x do the arithmetic
x = 14 by symmetry

11 = 15 - b
b + 11 = 15 - b + b add b to each side
b + 11 = 15 the b's on the right side cancel
b + 11 - 11 = 15 - 11 subtract 11 from each side
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