The answer would be B! This is because when multiplying 350 by .7, you are taking away the 30% which was originally part of the 350. Hope this helps!
To find what BDC is, you first have to solve for x. You can do this by creating an equation because you know what ADC equals:
6x + 7 + 12x - 3 = 112
18x - 4 = 112
+ 4
18x = 116
÷ 18
x = 6.44
Now you can substitute in 6.44 to find BDC:
12 × 6.44 = 77.33
77.33 - 3 = 74.33°, which is your answer. I hope this helps!
Let y = the length of the 3rd side
x+3 + 2x+4 + y = 6x
x + 2x + 3 + 4 + y = 6x
3x + 7 +y = 6x
7 + y = 3x
y = 3x - 7
The length of the third side in terms of x is 3x-7