6:4-89(65:90)

To simplify the given expression 6:4-89(65:90), we need to follow the order of operations:

1. Perform the division within the parentheses first: 65 ÷ 90 = 0.7222 (rounded to four decimal places).
2. Substitute the result back into the expression: 6:4 - 89(0.7222).
3. Perform the multiplication: 89 * 0.7222 = 64.2138 (rounded to four decimal places).
4. Subtract the result from the division operation from the first part of the expression: 6 ÷ 4 - 64.2138.
5. Finally, simplify the expression: 6 ÷ 4 - 64.2138 = 1.5 - 64.2138 = -62.7138 (rounded to four decimal places).

Therefore, the simplified result of 6:4-89(65:90) is approximately -62.7138.