If 7x - y = 23 and 7y - x = 31, then x + y =
(A) 4
(B) 6
(C) 7
(D) 8
(E) 9
Can some experts show me the best solution?
OA E
If 7x – y
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Adding together the two equations, we get:lheiannie07 wrote:If 7x - y = 23 and 7y - x = 31, then x + y =
(A) 4
(B) 6
(C) 7
(D) 8
(E) 9
(7x-y) + (7y-x) = 23 + 31
6x + 6y = 54
x+y = 9.
The correct answer is E.
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Hi lheiannie07,If 7x - y = 23 and 7y - x = 31, then x + y =
(A) 4
(B) 6
(C) 7
(D) 8
(E) 9
Let's take a look at your question.
$$7x-y=23\ ...\ \left(i\right)$$
$$7y-x=31\ ...\ \left(ii\right)$$
Adding Eq(i) and (ii),
$$7x-y+7y-x=23+31\ $$
$$6x+6y=54\ $$
$$6\left(x+y\right)=54\ $$
$$x+y=\frac{54}{6}=9$$
Therefore, Option E is correct.
Hope it helps.
I am available if you'd like any follow up.
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If we add the two given equations, we will have:lheiannie07 wrote:If 7x - y = 23 and 7y - x = 31, then x + y =
(A) 4
(B) 6
(C) 7
(D) 8
(E) 9
6x + 6y = 54
Divide both sides by 6, we have:
x + y = 9
Answer: E
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