Divide each side by 0.137 : N = M / 0.137 = 7.3 M (rounded)
Online or in a real book, you can look up the radius of Mars. Then write it in place of 'M' in this solution, and you'll have an actual number for the radius of Neptune.
The answer will be j because if it passes through o as a slope then your looking for your y intercept and -8 is your y intercept so your equation is y=0x+-8 in slope form