70-(81-39) :7+6*7 - 90:5+85:17

Let's break down the expression step by step: The expression is: \[ 70 - (81 - 39) : 7 + 6 * 7 - 90 : 5 + 85 : 17 \] 1. **Calculate the parentheses**: \[ 81 - 39 = 42 \] 2. **Rewrite the expression**: \[ 70 - 42 : 7 + 6 * 7 - 90 : 5 + 85 : 17 \] 3. **Perform the divisions**: \[ 42 : 7 = 6 \] \[ 90 : 5 = 18 \] \[ 85 : 17 = 5 \] 4. **Rewrite the expression**: \[ 70 - 6 + 6 * 7 - 18 + 5 \] 5. **Calculate \(6 * 7\)**: \[ 6 * 7 = 42 \] 6. **Rewrite the expression**: \[ 70 - 6 + 42 - 18 + 5 \] 7. **Perform the additions and subtractions from left to right**: - First, \(70 - 6 = 64\) - Then, \(64 + 42 = 106\) - Next, \(106 - 18 = 88\) - Finally, \(88 + 5 = 93\) The final result is: \[ \boxed{93} \]