[tex]Let \: x \: be \: the \: time \: which \: Laura \: worked \\ The \: time \: Tim \: worked:x - 10 \\ The \: time \: Eric \: worked:2x \\ We \: have \: an \: equation:x + x - 10 + 2x = 210 \\ < = > 4x = 220 \\ < = > x = 55 \: (hrs) \\ So \: Laura \: worked \: for \: 55 \: hours \: on \: the \: campaign.[/tex]