finding full formula of a compound knowing that it is a hydtrated sulfate salt of an alkali metal

Not very easy to do with no information other than what you posted.

I know but this is what my teacher gave us

To find the full formula of a compound that is a hydrated sulfate salt of an alkali metal, you need to consider the following steps:

Step 1: Identify the alkali metal
The alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Determine which alkali metal is present in the compound.

Step 2: Determine the sulfate group
The sulfate group is composed of one sulfur atom (S) and four oxygen atoms (O). Its charge is -2.

Step 3: Analyze the hydration state
The term "hydrated" indicates that water molecules (H2O) are present in the compound. The number of water molecules associated with the compound is usually indicated as a coefficient next to a dot, for example, H2O · x. Determine the value of x by considering the overall charge of the compound.

Step 4: Combine the elements
Based on the identified alkali metal and sulfate group, combine them in the ratio required to balance out the charges. Since alkali metals have a +1 charge and the sulfate group has a -2 charge, you will need two alkali metal ions per sulfate group to balance the charges. Include the appropriate number of water molecules based on the determined hydration state.

Step 5: Write the final formula
Write the formula using the chemical symbols and subscripts for each element and compound. For example, if the alkali metal is sodium (Na) and there are six water molecules associated with the compound, the full formula would be Na2SO4 · 6H2O.

By following the above steps, you can find the full formula of a compound that is a hydrated sulfate salt of an alkali metal.