1)
2x+y=1
5x+2y=0
у=1-2х
5х +2*(1-2х)=0
5х+2-4х=0
х= - 2
у= 1-2*(-2)=5
2)5+x>3x-3(4x+5)
5+х>3x-12x-15
x+9x>-5 - 15
10x>-20
x>-2