When A+B =13 and 2D+B = 13, what is the value of D?

13 2d13:51 Muv-Luv Regenerative Vol.04 Now Available, ... According to the staff, the film will be the first new 2D feature-length anime film in the franchise in nearly 30 years,Such structures often contain hh local densities of electronic charge carriers, giving rise to correlation phenomena and emerging properties