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The question is asking to balance the chemical equation. Balancing a chemical equation involves ensuring that the number of atoms of each element is the same on both sides of the equation. In the given equation, Al + HCl → H2 + AlCl3, we need to balance the number of atoms of each element. <br /><br />Looking at the equation, we can see that there are 1 Al atom, 1 H atom, and 1 Cl atom on the left side of the equation, and 1 Al atom, 2 H atoms, and 3 Cl atoms on the right side. To balance the equation, we need to adjust the coefficients (the numbers in front of the chemical formulas) to ensure that the number of atoms of each element is the same on both sides.<br /><br />The balanced equation is 2Al + 6HCl → 3H2 + 2AlCl3. This means that 2 Al atoms, 6 H atoms, and 6 Cl atoms are on the left side of the equation, and 3 H atoms and 2 Al atoms, 6 Cl atoms are on the right side of the equation. Therefore, the coefficients that balance the equation are 2, 6, 3, and 2.