We have an equation.
15-y=8
We will explain how we will use the Addition and Subtraction Properties of Equality to solve the equation. Let's first review these properties. They tell us that adding the same number to both sides of an equation or subtracting the same number from both sides results in an equivalent equation.
Also, notice that addition and subtraction are inverse operations — to undo one operation we can use the other one. Let's take a look at some examples.
In light of this information, we will solve the given equation by explaining how to use the Addition and Subtraction Properties of Equality. Since y is subtracted from the left-hand side, we can undo the subtraction by adding y to both sides of the equation using the Addition Property of Equality.
rcl
15- y+ y&=&8 + y
&⇓ &
15&=&8+y
Next, to get the term y alone, we will subtract 8 from both sides of the equation using the Subtraction Property of Equality.
rcl
15 - 8&=&8+y- 8&
&⇓ &
7&=&y
Finally, we can rearrange the equation to put it in the typical answer format.
7=y
⇓
y=7
Checking Our Answer
Checking Our Answer
We found that the solution of the equation is y=7. Now we will check whether we found the solution correctly. To do it, we will substitute 7 for y in the equation.
