Answer:
45
Explanation:
You already solved that the 2 angles of the triangle are 55° and since all of the angles are on a straight line, they add up to 180°
and the equation becomes...
3x-10+55=180
3x+45=180
Subtract 45 from both sides
3x=135
Divide by 3
x= 45
Then to double check you plug 45 as the value of x in.
3(45)-10+55=180
135-10+55=180
125+55=180
180=180