Answer:
Angle A = 19
Explanation:
Vertical angles are congruent ( equal to each other )
If angle A and angle B are vertical angles and vertical angles are congruent then angle A = angle B
If angle A = 3x + 13 and angle B = 5x + 9 then 3x + 13 = 5x + 9
( Note that we just created an equation that we can use to solve for x )
We now solve for x using the equation created
3x + 13 = 5x + 9
Step 1 subtract 3x from both sides
Outcome: 13 = 2x + 9
Step 2 subtract 9 from both sides
Outcome: 4 = 2x
Step 3 divide both sides by 2
Outcome: x = 2
Now to find Angle A
All we have to do to find the measure of angle a is simply substitute 2 for x in it's given expression ( 3x + 13 )
Substitute 2 for x
Angle A = 3(2) + 13
Multiply
Angle A = 6 + 13
Add
Angle a = 19