A) -3.1a + 2.25b - a - 1.4b + 6.3a = 2,2а +0,85b b) 3/8(2,4х-3,2у)-1,8(5/9х+1,5у) =3/8 * 12/5x - 3/8 * 16/5у - 9/5 * 5/9х - 9/5 * 3/2у = 9/10х - 6/5у - х - 27/10у = -1/10х -39/10у =-0,1х - 3,9у