C=x+9, c+x=99, c=99-x
So we have two equations equal to c, c=x+9 and c=99-x, since c=c:
x+9=99-x
2x+9=99
2x=90
x=45, and since c=x+9, c=54
So Charlie weighs 54 kg and his brother weighs 45 kg.
first get all variables on the same side, then use elimination to solve.
x = -3
y = -11
I would say 50/50 chance because it can go ether ways one can go heads the others can go tails
