Answer:
The subtraction property of equality
Option A is correct
Explanation:
The given equation is:
12 - x = 7x + 32
Subtract 12 from both sides
12 - 12 - x = 7x + 32 - 12
-x = 7x + 20 (Step 1)
From step 1 above, subtract 7x from both sides
-x - 7x = 7x - 7x + 20
-8x = 20 (Step 2)
Since we subtracted 7x from both sides to get step 2, the justification for step 2 is the subtraction property of equality
Using a system of equations, it is found that David is 12 years old.
<h3>What is a system of equations?</h3>
A system of equations is when two or more variables are related, and equations are built to find the values of each variable.
The variables are given as follows:
- Variable z: Rebecca's age.
David is three times younger than the dad and twice as old as Rebecca, then:
Rebecca is 30 years younger than the dad, hence:
z = y - 30.
Then, since x = 2z and z = y - 30 and y = 3x, we solve for x to find David's age.
x = 2(y - 30)
x = 2(3x - 30)
x = 6x - 60
5x = 60
x = 60/5
x = 12.
David is 12 years old.
More can be learned about a system of equations at brainly.com/question/24342899
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Answer:
Step-by-step explanation:
100.5 in ^2
The answer is 49.89
hope this helped:)
