1) 1/6 - (5/12 - 7/12)
= 1/6 - (-2/12)
= 1/6 + 2/12
= 1/6 + 1/6
= 2/6
= 1/3

2) -13 - (20 - 32)
= -13 - 20 + 32
= -33 + 32
= -1

3) -4.5 - (7 - 9.5)
= -4.5 - (-2.5)
= -4.5 + 2.5
= -2.0