Let's break down the given expression step by step:

First, we need to calculate cos(40º):
cos(40º) ≈ 0.766

Next, we need to calculate sin(50º):
sin(50º) ≈ 0.766

Now, we need to calculate cos(80º):
cos(80º) ≈ 0.173

Lastly, we need to calculate sin(70º):
sin(70º) ≈ 0.940

Substitute these values into the expression:
(0.766 + 0.766) / (0.173 - 0.940)
= 1.532 / -0.767
= -2

Therefore, the value of the expression cos(40º) + sin(50º) / cos(80º) - sin(70º) is -2.