Answer = 4.5
Rationale:
the element Mg comes with a 2+ ion and NO3 comes with -1 ion thus 3 * 1.5 M = 4.5 basically look up what mg ion is on google and it says mg+2 and no3 ion no3- im assuming you cant though so look at the formula.
Mg(NO3)2, mg gave 2 to NO3 but where is mg's number? its 1 so 2+1 = 3
* # M = ans
