IXL | Identify equivalent equations

Select all of the equations below that are equivalent to:

10 + k = 15

Use properties of equality.

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question

Select all of the equations below that are equivalent to:

9 = n + 15

Use properties of equality.

key idea

The Subtraction Property of Equality says that if you subtract the same number from both sides of an equation, then the two sides are still equal.

solution

Go through the answer choices one by one.

First, take

13 = n + 15 + 4

. Is it equivalent to

9 = n + 15

n + 15 + 4

Subtract 4 from both sides

13 − 4

n + 15 + 4 − 4

Subtract 4 from both sides

Simplify

n + 15

Simplify

Yes,

13 = n + 15 + 4

is equivalent to

9 = n + 15

.

Second, take

18 = n + 15 + 9

. Is it equivalent to

9 = n + 15

n + 15 + 9

Subtract 9 from both sides

18 − 9

n + 15 + 9 − 9

Subtract 9 from both sides

Simplify

n + 15

Simplify

Yes,

18 = n + 15 + 9

is equivalent to

9 = n + 15

.

Third, take

9 + 3 = n + 18

. Is it equivalent to

9 = n + 15

9 + 3

n + 18

Subtract 3 from both sides

9 + 3 − 3

n + 18 − 3

Subtract 3 from both sides

Simplify

n + 15

Simplify

Yes,

9 + 3 = n + 18

is equivalent to

9 = n + 15

.

Fourth, take

9 + 4 = n + 19

. Is it equivalent to

9 = n + 15

9 + 4

n + 19

Subtract 4 from both sides

9 + 4 − 4

n + 19 − 4

Subtract 4 from both sides

Simplify

n + 15

Simplify

Yes,

9 + 4 = n + 19

is equivalent to

9 = n + 15

According to the Subtraction Property of Equality, these equations are equivalent to

9 = n + 15

13 = n + 15 + 4

18 = n + 15 + 9

9 + 3 = n + 18

9 + 4 = n + 19

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M.5Properties of equality

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