First divide the equation by 3 to find the number of moles of Li₃PO₄ required to react with one mole of Ca(NO₃)₂

Next, multiply the equation by 3.4 (we have 3.4 moles of Ca(NO₃)₂) , this gives the theoretical amount of Li₃PO₄.
Now compare the actual moles of Li₃PO₄  with the theoretical value.
If the theoretical is less than the actual then there is sufficient of this reagent.
If the theoretical is greater than the actual then this is the limiting reagent.