(a) We have to find the solution of given question:

= 35 – (20)

= 35 – 20

= 15

Hence, answer is 15

(b) We have to find the solution of given question:

= 72 – (90)

= 72 – 90

= - 18

Hence, answer is – 18

(c) We have to find the solution of given question:

= (- 15) – (- 18)

= - 15 + 18

= 3

Hence, answer is 3

(d) We have to find the solution of given question:

= (- 20) – (13)

= - 20 – 13

= - 33

Hence, answer is – 33

(e) We have to find the solution of given question:

= 23 – (- 12)

= 23 + 12

= 35

Hence, answer is 35

(f) We have to find the solution of given question:

= (- 32) – (- 40)

= (- 32) + 40

= 8

Hence, answer is 8