3 b 7 c 8 and 3 a 4 b 2 c . 2a and −5a. −3a and −4b. −ab and a3b2. −2ab4 and −5a4bc. −2x6y3z and −6xy2z. 3a2b, −5ab2, and −7a4b2. 2a2bc3, −3a3b2c, and −ab2c3. 2b2c2x2, 2a2b2c3, and −3a3bx3. 2a3b2c, −3a2b3c, and −4a2bc3. 7am2x3, 3a4m2x3, and −2amx.