If 3x +5y + 7z = 49
9x + 8y + 21z = 126,
then find the value of 2y.
Answer & explanation
Correct answer: option 3
We have two equations and 3 variables
So, put z = 0 (because z is extra)
3(3x + 5y = 49) (Multiply by 3 for making 9x)
9x + 8y = 126
9x + 15y = 147 ...(i)
9x + 8y = 126 ...(ii)
Eq.(i) - Eq. (ii)
(9x + 15y) - (9x + 8y) = 147 - 126
9x + 15y - 9x + -8y = 147 - 126
7y = 21
y = 3
2y = 6