The sum of the angles on a straight line is 180 degrees. This means that
angle MJO + angle NJO = 180
From the information given,
angle MJO = 131
angle NJO = 15x + 4
Thus,
131 + 15x + 4 = 180
135 + 15x = 180
15x = 180 - 135 = 45
x = 45/15
x = 3
We would substitute x = 3 into angle NJO = 15x + 4
angle NJO = 15 * 3 + 4 = 45 + 4
angle NJO = 49
