On applying the BODMAS rule, we get:
36 [18 { 14 (15 4 ÷ 2 × 2)}]
= 36 − [18 − {14 − (15 − 2 × 2)}] (On performing division)
= 36 [18 {14 (15 4)}] (On performing multiplication)
= 36 [18 {14 11}] (On simplifying parentheses)
= 36 [18 3] (On simplifying braces)
= 36 15
= 21