Question 1156637

let Dave's age be {{{x}}} and his sister's age {{{y}}}

if Dave is {{{4}}} years older than his sister May, we have

{{{x=y+4}}}.......eq.1

 
if their ages are added together the sum is {{{14}}}, we have

{{{x+y=14}}}.....eq.2....substitute {{{x}}} from eq.1

{{{y+4+y=14}}}

{{{2y=14-4}}}

{{{2y=10}}}

{{{y=5}}}

go to

{{{x=y+4}}}.......eq.1, substitute {{{y}}}

{{{x=5+4}}}

{{{x=9}}}


so, Dave's is {{{9}}} years old, and his sister May is {{{5}}} years old