Step 1) Find the slope of the given equation ... I'm having trouble reading your question, is it 2/3rds?
Step 2) Find the negative reciprocal of the answer to step 1) ... -3/2 ... because perpendicular lines
have slopes that are negative reciprocals.
Step 3) Use the point intercept form for a line to find the needed equation.
y - y1 = m(x - x1) ---> y - 8 = -3/2(x - -1)
Step 4) Simplify the equation from step 3) and solve for y.