640-110•(90:18)

To solve this expression, we can follow the order of operations which is parentheses, multiplication/division from left to right, and then addition/subtraction from left to right.

First, let's simplify the expression inside the parentheses: 90 divided by 18 equals 5. Therefore, our expression becomes: 640 - 110 • 5.

Next, we perform the multiplication: 110 multiplied by 5 equals 550. Now, we have: 640 - 550.

Finally, we subtract: 640 minus 550 equals 90.

Therefore, the result of the expression 640-110•(90:18) is 90.