Answer: 76 degrees
In order to solve for the ? Angle you can use inverse tangent with our given sides
The original equation for inverse tangent is tan^(angle)=opposite/hypotenuse, so plug the values in, and isolate the angle by dividing tangent. Then solve on a calculator and let x=?; tan^-1(40/10) which is equal to 75.96375653 which is approximately 76 degrees