a) 4x²*3y³ = 4*3*x²*y³ = 12x²y³
b) 0.2a*1/2c²*(-7b) = 0.2a*0.5c²*(-7b) = 0.2*0.5*(-7)*a*c²*b = -0.7c²ab
c) (-a)²*(-a)³ = -1a⁵
d) -3/2ab²*(6ac)²= -1.5*36*a*a²*b²*c² = -54a³b²c²
e) -1.2m²n*0.3m = -1.2*0.3*m²*m*n = -0.36m³n
f) -3bc³*(-y⁴)*5/9 b²y = -3*5/9*b*b²*c³*y*(-y⁴) = -5/3 b³c³y⁵
