Ialready give you the answer for number 19 but can you explain. and then can you tell me what question number 20 is and explain to. you!

So, You know the outer angle, so you need to know the inner angle on <B. so 180-148 is 32. since you know two of the inside angles, and all triangle angles add up to 180 degrees, take 32+83, which is 115, and subtract that from 180, which is 65
Hope this helps!
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What's the denominator