Question 19
The steps to solve three equations are shown below. Identify and correct any mistakes.
(a)
(b)
(c)
We will check each equation step by step to find any errors and then solve them correctly.
Step 1 — Equation (a) Analysis
Let us look at the first equation. The given equation is . The next step shown is . This step is wrong. To get from , we divide by 6. But we must divide all terms by 6. Here, only and were divided by 6. The number 9 was not divided by 6. So, this is a mistake.
Let us solve it correctly. First, we move the number 9 to the other side. We subtract 9 from both sides of the equation. Now, we want to find . We divide both sides by 6. We can simplify this fraction. Both 57 and 6 can be divided by 3. We can write this as a mixed number.

Step 2 — Equation (b) Analysis
Let us look at the second equation. The given equation is . The next step shown is . This step is correct. All terms were divided by 2. Then, 12 was subtracted from both sides. Finally, both sides were divided by 7. All steps are correct. There is no error in this solution.
Step 3 — Equation (c) Analysis
Let us look at the third equation. The given equation is . The next step shown is . This step is wrong. When we move -5 from the left side to the right side, its sign must change. It should become +5, not -5. So, this is a mistake.
Let us solve it correctly. First, we move the number -5 to the other side. We add 5 to both sides of the equation. Now, we want to gather all terms on one side. We subtract from both sides. Finally, we want to find . We divide both sides by -5. We can write this as a mixed number.
Answer
(a) The mistake was in dividing only some terms by 6. The correct answer is . (b) There were no mistakes in the given steps. The answer is . (c) The mistake was in changing the sign of -5 incorrectly when moving it. The correct answer is .
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