(20.88 : 18+45:0.36):(19.59+11.95)

Assuming colon (:) means division:

• (20.88 ÷ 18) + (45 ÷ 0.36) = 1.16 + 125 = 126.16
• (19.59 + 11.95) = 31.54
• Then 126.16 ÷ 31.54 = 4 (since 31.54 × 4 = 126.16)

Answer: 4