’g = (r - g )/(1 + d)‘ is a typing error, it should be g = (r - d)/(1+d) with d being the dividend yield. Also note that Bradley suggests using industry’s d and r.
by using algebra, you can prove that indeed g = (r-d)/(1+d)
use the alternative explanation where they plug in numbers instead of using letters as notations if it confuses you.