Hello! A triangle has angles that sum up to 180°. So first off, let's solve for the angle of the other triangle. 83 + 31 gives us 114. 180 - 114 is 66. So the angle for the first triangle is 66°. The opposite angle would be the same. Finding the measurement of the other triangle gives us the measurement of x, because the angles are the same. So x = 66°.