The answer is 75°.
Ok, now I am going to walk you through step-by-step so hopefully this will make more sense :)
We know that ADC=134°, so if we were to add the two angles that make it up together, their sum should equal 134°.
So if we wanted to write that out it would look like this:
(5x+4)+(7x-2)=134°.
Now we can add like terms, so add the x's together and add the regular numbers together. This means we do 5x+7x=12x and 4-2=2. The simplified equation should now look like this:
12x+2=134°.
We can now subtract 2 from both sides, then to get x alone, we divide 132 by 12. To write it out it looks like this:
12x=132°, then x=11.
Now that we know x, we can plug it into the value of BDC, so:
7(11)-2. 7×11=77 and 77-2= 75°
Hope this helps!
