2 method questions Im confused on

1.If you use the elimination method to solve the system of equations
3x - 4y = 9 and 2x + 3y = 7, which of the following would be the best method?

Method I: Multiply both sides of the first equation by 2, and multiply both sides of the second equation by 3. Then add the two equations.

Method II: Multiply both sides of the first equation by 3, and multiply both sides of the second equation by 4. Then add the two equations.
A. Method I
B. Method II
C. Both method I and II
D. neither method I nor II

2.If you use the substitution method to solve the system of equations
3x - 2y = 4 and x + y = 5, which of the following would be the best method?

Method I: Solve the second equation for x, and substitute 5 - y for x into the first equation.

Method II: Solve the second equation for y, and substitute 5 - x for y into the first equation.
A. Method I
B. Method II
C. Both method I and II
D. neither method I nor II

1. Method 1 doesn't work as 2(3x) + 3(2x) doesn't cancel. So the answer would be B.

2. C: Both work fine.

3x - 4y = 9
2x + 3y = 7

2(3x - 4y) = 18
3(2x + 3y) = 21

6x - 8y = 18
-
6x + 9y = 21
-------------------
y = - 4

2x + 3*(-4) =7
2x - 12 = 7
2x = 19
x = 19/2

ans: {19/2; - 4}


2) 3x - 2y = 4
x+ y = 5, x = 5 - y

3(5 - y) - 2y = 4
15 - 3y - 2y = 4
15 - 5y = 4
11 = 5y
y = 11/5

x + 11/5 = 5
x = 5 - 11/5
x = 25/5 - 11/5
x = 14/5

ans : ( 14/5 ; 11.5)

u r far smart enough. It doesn't matter u use method 1 or 2. But method make difference in time

use elimination and both method 1 and method 2 take equally time u can try..

Method 1 works if you subtract rater than add the equations and method 2 works as is

Both methods work