how many days required for A,B,C if they work together

Question

If,A &B take 12days to complete a work, A&C take 15 days and B&C will take 20 days to complete the same work then how many days required for A,B&C to complete the same work together..

Answer 1

??????????????? "slope kontaening points" ????????????? . . . yu have 2 points, so yukan make a strate line tween points . . . . points: (4,2) & (7,1) . . . deltax=3, deltay=-1, slope=deltay/deltax=-1/3 . . . y=-(1/3)x + konst . . . projekt line from x=4 tu x=0...deltax=-4 . . . deltay=slope*deltax=-(1/3)*(-4)=+4/3 . . . y at x=0...2+4/3=10/3 . . . y=-(1/3)x+10/3