The best answer is a, 20.78 units. You can use the Pythagorean theorem to solve this: a^2+b^2=c^2. Just plug in the variables and solve it as a multi step equation. The legs of the right triangle are a and b, which in this case you would plug in those variables with x and 12. The hypotenuse is c, which in this case is 24. That will leave you with 12^2+b^2=24^2. Simplify those exponents and continue solving for b. At the last part of your equation solving, you’ll be left with b^2= a number. To find the value of b just find the s quake root of that number and there’s your answer.
sry im being Dumb im pretty sure its 180 because intersecting lines form vertical angles if those angles are acute the one in between is obtuve a like is 180 degrees