9/10-(1/12+2/15)
=9/10-(1/3-1/4+1/3-1/5)
=9/10-(2/3-1/4-1/5)
=9/10-2/3+1/4+1/5
=9/10-2/3+9/20
=9/10+9/20-2/3
=27/20-2/3
=81/60-40/60
=41/60