Question

I had help but still don't understand plz help

Answer 1

Two  parallel lines are intersect by the same line, and the angles shown lie on the same orientation about the intersection so the angles are equal to each other...which means:

9x+21=10x+10  subtract 21 from both sides

9x=10x-11  subtract 10x from both sides

-x=-11 divide both sides by -1

x=11