Question

I don't know which one please help

Answer 1

The angle of a straight line is 180°
so you can add both angle sides and equate it to 180°
(6x - 10) + (6x + 10) = 180
join like terms
6x + 6x -10 + 10 = 180
12x = 180 (-10 and +10 cancels out)
$\frac{12x}{12} = \frac{180}{12}$
(12 and 12 cancels out)
x = 15
Your answer will the the first option
a) x = 15

Answer 2

The answer is (A) 15. 

(6x -10) makes 80 and (6x+10) makes 100

together that equales 180 degrees. since it is a straight line the sum of the the two would have to equal 180. hope this helped :D