If 5a + 6c – 5b = 25 and c – 2b + 2a = 3 (where a, b and c are real numbers), then the value of c(b−a) is equal to यदि 5a + 6c – 5b = 25 तथा c – 2b + 2a = 3 (जहाँ a, b व c वास्तविक संख्याएं हैं), तब c(b−a) का मान है