Подобные слагаемые: ж) 0,3а-0,2b-0,7a+0,2b з) 4a-6a-2a+12-11 и) 2/3a+3/8b-1/6a-1/4b

Ж) 0,3a - 0,2b - 0,7a + 0,2b = (0,3a - 0,7a) + (0,2b - 0,2b) = - 0,4a
з) 4a - 6a - 2a + 12 - 11 = (4a - 6a - 2a) + (12 - 11) = - 4a + 1
и) 2/3a + 3/8b - 1/6a - 1/4b = (2/3a - 1/6a) + (3/8b - 1/4b) = (4/6a - 1/6a) + (3/8b - 2/8b) = 3/6a + 1/8b = 1/2a + 1/8b

Пояснения:
2/3 = (2*2)/(3*2)а = 4/6 - доп.множ. 2
1/4 = (1*2)/(4*2) = 2/8 - доп.множ. 2
3/6 = (3:3)/(6:3) = 1/2 - сократили на 2

Ж) (0.3a и -0.7a)(-0.2b и 0.2b);з)(4a,-6a,-2a)и(12,11);и)(2/3a,1/6a)и(3/8b,1/4b)