Question 918657
5x -7y =4
7x- 3y =4 
------------
Multiply the 1st eqn by 3 and the 2nd by -7
---
15x - 21y = 12
-49x+ 21y = -28
-------------------------- Add
-34x = -16
================
solve for x, then sub and solve for y.
============
============
The addition method is multiplying 1 or both eqns by something to make the coefficients of one of the variables equal, then eliminating it.