The average of X₁, X₂ and X₃ is 14. Twice the sum of X₂ and X₃ is 30. What is the value of X₁?

$$\eqalign{ & {{\text{X}}_1} + {{\text{X}}_2} + {{\text{X}}_3} \cr & = \left( {14 \times 3} \right) \cr & = 42 \cr} $$
According to the question,
$$\eqalign{ & 2\left( {{{\text{X}}_2} + {{\text{X}}_3}} \right) = 30 \cr & \Rightarrow {{\text{X}}_2} + {{\text{X}}_3} = 15 \cr & \therefore {{\text{X}}_1} = \left( {42 - 15} \right) = 27 \cr} $$