Featured Puzzle: Mathrax #1

Mathrax originated on the German puzzle website janko.at. Fill in numbers from 1 to 7, such that no row or column contains any duplicate numbers. Sounds pretty normal so far, right? Now let’s add math!

• Circles contain arithmetic clues with a number and an operator, or the letters E or O.
• If the circle contains an E or O, the numbers in all four of the cells surrounding it are all even, or odd, respectively.
• A circle with a number and operator shows the result when that operator is applied to digits in opposite corners.

For example, a circle containing (2-) might have 5 in the upper left, 7 in the upper right, 9 in the lower left, and 3 in the lower right.

This results in 5-3 = 2 along one diagonal, and 9-7 = 2 along the other.