A drawing for clearer illustration is shown below
Looking at the diagram above, angle 105 and angle y are vertically opposite angles. Vertically opposite angles are equal. This means that
angle y = 105 degrees
Angle y and angle (x + 112) are on the same side of the transversal and they are in similar positions. This means that they are corresponding angles. Corresponding angles are equal. Thus,
x + 112 = 105
x = 105 - 112
x = - 7
