Question

If m ZABD = 78°, what are mZABC and mZDBC? (5x+3) (5x-5)

Answer 1

ABD = ABC + DBC
Eqivalent to:
78 = (5x + 3) + (5x - 5)
78 = 5x + 5x + 3 - 5
78 = 10x - 2
80 = 10x (move -2 to the left side and get 78 + 2 = 80)
8 = x (80/10 = 8)
With x = 8,
ABC = 5x - 5 = 8*5 - 5 = 40 - 5 = 35
DBC = 5x +3 = 8*5 + 3 = 40 + 3 = 43

Answer 2

Hi, I'm happy to help!

First, we need to solve for x. We know that ABD is 78 degrees. (5x+3), and (5x-5) combined are also 78 degrees. So, we combine the like terms of these to get a new expression.

(5x+3) +(5x-5)

10x-2=78

From here, we want to single out the x, by editing both sides in the same way.

10x-2=78

    +2  +2

10x=80

÷10 ÷10

x=8

Now that we know what x is, we can plug it in to the previous expressions to get the angles of ABC and DBC.

(5x-5)

((5·8)-5)

(40-5)

35

Now, we know that ABC is 35 degrees.

(5x+3)

((5·8)+3)

(40+3)

43

Now, we also know that DBC is 43 degrees.

To verify our answer we can add ABC and DBC together to check if it totals to ABD.

35+43=78

Now, we know that the answer: ABC is 35 degrees and DBC is 43 degrees is correct.

I hope this was helpful, keep learning! :D