Mr$AlCl3$ = 27 $Al$ + 3$35.5$ = 27 + 106.5 = 133.5Mr$Fe(OH)3$ = 56 $Fe$ + 3$16+1$ = 56 + 51 = 107Mr$PH3$ = 31 $P$ + 3$1$ = 31 + 3 = 34

Итак:

Mr$AlCl3$ = 133.5Mr$Fe(OH)3$ = 107Mr$PH3$ = 34