(2/3) / 3 = 1/x...2/3 to 3 lawns = 1 to x lawns
cross multiply
(2/3)(x) = (3)(1)
2/3x = 3
x = 3 * 3/2
x = 9/2 or 4 1/2 lawns can be cut with a full tank of gas
The answer to this question is: 15
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.
