2y + x = 9, (1)
3y - 5x = 20. (2)
Multiply equation (1) by 5 (both sides). You will get an equivalent system
10y + 5x = 45, (3)
3y - 5x = 20. (4)
Add the equations (3) and (4). The terms with "x" will cancel, and you will get
13y = 45 + 20 = 65, ----> y = = 5.
Then from the equation (1) x = 9 - 2y = 9 - 2*5 = 9 - 10 = -1.
Answer. x= -1, y=5.
Solved.
The method I applied is called "the Elimination method".
