Write an equation, in slope-intercept form, to model each sitution. : the population of pine bluff is 6791 and is decreasing at the rate of 7 per year.

Y = -7x + 6791 

So since it's decreasing we know that it'll be a negative. It decreases by 7 pine bluffs per year. We can use that equation to model the situation. 
But let me show you an example to prove it. 

Lets say we want to know how many pine bluffs there would be in 3 years
y = -7(3) + 6791 
y = -21 + 6791 

The -21 is the total amount lost in those 3 years, but we have to subtract it from the original amount which was 6791 

y = -21 +6792 
y = 6770
In three years there would only be 6,770 pine bluffs.

6791 of per year answer

the theorem is SAS that proves the two triangles are congruent