If 3x + 5y +7z = 49 and 9x + 8y + 21z = 126, then what is the value of y?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 3
3x + 5y +7z = 49
Multiplying by 3 on both the sides
9x + 15y + 21z = 147 eq1
9x + 8y + 21z = 126 eq2
eq1 - eq2
7y = 21
y = 3