You can
put this solution on YOUR website!let m="man now" and s="son now"
"A man will be three times as old as his son will be in nine years" ___ m+9=3(s+9)
"he is six times as old as his son is now" ___ m=6s
"how old is the SON?" ___ substituting ___ (6s)+9=3(s+9)
expanding ___ 6s+9=3s+27
subtracting 3s+9 ___ 3s=18
dividing by 3 ___ s=6