a)
Step 1: Problem
write an equation of the line with slope 7 and Y-intercept -9.
Step 2; Concept
Equation of a line y = mx + c
Step 3: Method
Given data
Slope m = 7
Intercept c = - 9
Therefore, the equation of a line
y = mx + c
y = 7x - 9
Step 4: Final answer
y = 7x - 9