So hmm notice the first picture, that's the "inscribed angle theorem", as you'd know
now, notice angle 2 in yours on the second picture
R=10
because 10 divided by ten =1 +4 =5
Answer: 18
Step-by-step explanation: The formula for calculating a triangle’s area is 1/2(base•height). This means that 12•3 is 36, which multiplied by 1/2 is 18.
(Hope this helps)