{2x-7y = 3 5x + 3Y = - 13 binary once addition and subtraction method I can't figure it out after 2 days. I hope you can help me solve this problem

{2x-7y = 3 5x + 3Y = - 13 binary once addition and subtraction method I can't figure it out after 2 days. I hope you can help me solve this problem

The first equation is multiplied by 5 and the second by 2. Then the two equations are subtracted to eliminate X. the rest is y. 41Y = - 41. So y = - 1;
Substituting y into any formula, we get x = - 2

X + y + Z = 6, 3x-y + 2Z = 12, x-y-3z = - 4, how to solve this system of linear equations of three variables!

The results are: 1 + 2, 4x + 3Z = 18, 4
① + 3, 2x-2z = 2, 5
④ And (5) constitute the equations
Solving this system of equations, we get x = 3, z = 2
Substituting it into the equation (1) which is convenient for calculation, we get y = 1
The solution of this system is x = 3, y = 2, z = 1
Note: in order to transform the ternary system of linear equations into binary system of linear equations, each equation in the original system should be used at least once

If x = 2, y = 1 for the system of quadratic equations 2x-y = m, x + my = n, then | M-N | is?

2x-y=m
x+my=n
Substituting x = 2, y = 1, we get the following result
4-1=m
Substituting M = 3 into x + my = n
2+3*1=n
n=5
m-n=3-5=-2
|m-n|=|-2|=2