Because this is an isosceles triangle, we know that the bottom two angles are equal. We also know that the sum of the angles inside a triangle will always come to 180°. With that in mind, we can simply subtract 38° from 180° and divide by two to get the correct answer.
B, because you subtract 9 from both sides(2x-9 leaves 2x by itself then 33-9=24), which leaves you with 2x=24 the you divide everything by 2 which leaves you with x=12
