5(3a²b)-4(-ab²+3a²b)
=15a²b+4ab²-12a²b
=3a²b+4ab²
=3(-1/2)²(-1/3)+4(-1/2)(-1/3)²
=3(1/4)(-1/3)+4(-1/2)(1/9)
=(-1/4)+(-2/9)
=-17/36