0
C - 6C + 7 = -5C + 7
7 * (c + 2) = 7 * c + 14
If C is co-prime with 6 and with 7, then LCM(6, 7, C) = 42*C
If not, the answer depends on the value of C.
7=c(s) obviously
7 C in the W = 7 Continents in the World.