4) -3.6x+6-4+4.6x+1.2x-6 = 2.2x-4 =( -22/10 × 15/22) - 4 = -1.5 - 4 = - 5.5

5) x= 3y-9

0.9x - 0.7x - 0.6y = 0.3x - 0.6y =

= 0.3( 3y-9) - 0.6y = 0.9y - 2.7 - 0.6y =

=0.3y - 2.7