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

Let's break down the expression step by step according to the order of operations (PEMDAS/BODMAS). The expression is: \[ 70 - (81 - 39) : 7 + 6 * 7 - 90 : 5 + 85 : 17 \] 1. **Parentheses first**: Calculate \( (81 - 39) \). \[ 81 - 39 = 42 \] 2. **Now substitute this back into the expression**: \[ 70 - 42 : 7 + 6 * 7 - 90 : 5 + 85 : 17 \] 3. **Next, perform the division**: - Calculate \( 42 : 7 \): \[ 42 ÷ 7 = 6 \] - Calculate \( 90 : 5 \): \[ 90 ÷ 5 = 18 \] - Calculate \( 85 : 17 \): \[ 85 ÷ 17 = 5 \] 4. **Substituting these values back** into the expression gives: \[ 70 - 6 + 6 * 7 - 18 + 5 \] 5. **Next, perform multiplication**: - Calculate \( 6 * 7 \): \[ 6 * 7 = 42 \] 6. **Substituting this value in**: \[ 70 - 6 + 42 - 18 + 5 \] 7. **Now perform addition and subtraction from left to right**: - First, \( 70 - 6 = 64 \) - Then, \( 64 + 42 = 106 \) - Next, \( 106 - 18 = 88 \) - Finally, \( 88 + 5 = 93 \) So, the final result of the expression is: \[ \boxed{93} \]