since the angles seem similar they're most likely to be the same but since its 3x and you have to find the value of x then we will do 3 x ?=30, which is 10. if you want to check there is one way, since the angle on a straight line is 180 you can do 180 - 30 =150 which will be the unknown value next to the given angle. Since the unknown angle is on the line with the 150 degree angle we can do 180 - 50 to get the unknown angle (3x) which is 30. So in conclusion x will be 10