Question:
If $3x + 4y = 12$ and $x - y = 1$, what is the value of $x + y$?
If $3x + 4y = 12$ and $x - y = 1$, what is the value of $x + y$?
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Simultaneous equations can be solved by substitution or elimination. Always verify by substituting back.
Updated On: Aug 1, 2025
24/7
25/4
25/7
23/7
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The Correct Option is C
Solution and Explanation
Step 1: From the Second Equation
From x − y = 1:
x = y + 1
Step 2: Substitute into the First Equation
Substituting x = y + 1 into 3x + 4y = 12:
3(y + 1) + 4y = 12 3y + 3 + 4y = 12 7y + 3 = 12 7y = 9 y = 9/7
Step 3: Find x
Using x = y + 1:
x = (9/7) + 1 = (9/7) + (7/7) = 16/7
Step 4: Find x + y
Adding the values:
x + y = (16/7) + (9/7) = 25/7
Final Answer:
x + y = 25/7
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