How is subtracting -4x from 9x similar to subtracting -4 from 9?

You are subtracting four of one thing from nine of it, even if one is four of x and the other is four ones, the actual number four. It's like doing math with strawberries like people do to explain it to little kids, but instead of strawberries, it's a placeholder for an unknown but constant value.

When you have two variables which in this case is X, they are the same and you would treat it the same as a regular subtraction problem

3.80*10⁻³ moles of HCl can be produced from 0.226 g of SOCl₂

Explanation:

The balanced reaction is:

SOCl₂ + H₂O ----> SO₂ + 2 HCl

By stoichiometry of the reaction they react and produce:

SOCl₂: 1 moleH₂O: 1 moleSO₂: 1 moleHCl: 2 mole

Being:

S: 32 g/moleO: 16 g/moleCl: 35.45 g/moleH: 1 g/mole

the molar mass of the compounds participating in the reaction is:

SOCl₂: 32 g/mole + 16 g/mole + 2*35.45 g/mole= 118.9 g/moleH₂O: 2*1 g/mole + 16 g/mole= 18 g/moleSO₂: 32 g/mole + 2*16 g/mole= 64 g/moleHCl: 1 g/mole + 35.45 g/mole= 36.45 g/mole

Then, by stoichiometry of the reaction, the following amounts of mass react and are produced:

SOCl₂: 1 mole* 118.9 g/mole= 118.9 gH₂O: 1 mole* 18 g/mole= 18 gSO₂: 1 mole* 64 g/mole= 64 gHCl: 2 mole* 36.45 g/mole= 72.9 g

Then the following rule of three can be applied: if by stoichiometry of the reaction 118.9 grams of SOCl₂ produce 2 moles of HCl, 0.226 grams of SOCl₂ how many moles of HCl do they produce?

moles of HCl= 3.80*10⁻³

3.80*10⁻³ moles of HCl can be produced from 0.226 g of SOCl₂