How do you find the slope intercept form for (1,-5) ; slope -3/2

The slope-intercept form can be shown by the following formula:
y = mx + b

 - Where "mx" is the slope; in your situation, it would be -3/2x.

 - And "b" is the y-intercept, where the line intercepts at the y-axis; in this case, it is currently unidentified

We are going to have to use the Point-Slope form to find the rest of the variables, the formula is: (y - y1) = m(x - x1)

We know these variables: 
x = 1
y = -5
slope = -3/2x

This is the equation after we plugin in the variables that we have:

#1    Then we solve.
#2   y + 5 = -3/2x + 3/2
#3   y = -3/2 - 3.5

The answer would be: 

the answer would be c ≈ 18.852*3.14= 6.286.28*3=18.85