78, because you have to do the inverse operation so 80/2= 40 then 40-1= 39 and 39*3 = 78
-1, because the equation for the slope is y2-y1/x2-x1. So let's bring the y value in the second set of point, which is 20, and bring the first y value in the first set of points, which is 5. 20-5 is 15. Now let's subtract the x values. So the second x from the second parentheses x value is -7, and the first x value from the first parentheses is 8. -7-8 is -15. Now we have this division equation, 15/-15, which is -1. So therefore, the slope of the line will be -1.
So if <AED =100 degrees result <BEC = 100 degrees too and 360-200=160
so 160/2 = 80 what mean that angle DEC=80 degrees
hope helped
