Explanation:
first you need to know that angle 4 and angle d are the same measurement. so then you have to notice that a straight line is equal to 180 degrees. by knowing this you can make this equation
x+30+ 2x +15= 180
next combine like terms:
3x+ 45=180
next subtract 45 from both sides
3x=135
next divide by 3 on both sides to get x alone. this will give you your answer.
x=45
once you know this plug 45 into you equation to do d the value of the angle 4