5(3a²b-ab²)-4(-1/2*ab²+1/3*a²b)=15a²b-5ab²-(-2ab²+4/3*a²b)=15a²b-5ab²+2ab²-4/3*a²b=(15a²b-4/3*a²b)-(5ab²-2ab²)=41/3*a
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