Answer:
x=7
Step-by-step explanation:
The angle of a straight line is 180 degrees, so let's just say the other angle to the right of 15x+34 is "a" that means that 15x + 34 + A = 180, and since the sum of interior angles of a triangle is 180 degrees, that means that 29 + A + 12x + 26 = 180, and we can define A using this equation in terms of x.
Original equation (sum of interior angles)
A + 29 + 12x + 26 = 180
Combine like terms
A + 12x + 55 = 180
Subtract 12x and 55 from both sides
A = -12x + 125
Original equation (since a line is 180 degrees)
15x + 34 + A = 180
Substitute -12x + 125 as A
15x + 34 + (-12x + 125) = 180
Combine like terms
3x + 159 = 180
Subtract 159 from both sides
3x = 21
Divide both sides by 3
x = 7
