(9b^2 - 49) * (1/3b-7 - 1/3b+7) + b-13
B=345

(9в² - 49) *  (1/(3в-7) - 1/(3в+7)) + в-13 = = (3в-7)(3в+7) * (1/(3в-7) - 1/(3в+7)) + в-13 = = (3в+7 + 3в-7) + в-13 = 3в + 3в + в - 13 = 7в - 13,при в = 345:  7 * 345 - 13 = 2415 - 13 = 2402