Please help me with this math problem ASAP :)

Your answer is «BDC = 70°
Step-by-step explanation:
So you know that the total angle is 150°. Given
that, we can set the two equations equal to 150°
because we know that they add to 150°.
-3x +34+-2x +56=150
First, combine the like terms.
-3x - 2x=-5x
34 + 56 = 90
-5x + 90 = 150
Get the -5x by itself by subtracting 90 from 150.
150 - 90 = 60
Now you have:
-5x = 60
Get the x alone by dividing both sides by -5.
-5x/-5 = 1x (written as just ×, though)
60/-5 = -12
Therefore, X=-12.

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table