Question 709552
let Tony's age be {{{x}}} and Julia's age {{{y}}}

if Tony is {{{4}}} years older than Julia, then

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


if the sum of their ages are their ages is {{{30}}}, then

{{{x+y=30}}}.....eq. 2..substitute {{{x}}} from eq. 1

{{{y+4+y=30}}}......solve for {{{y}}}

{{{2y=30-4}}}

{{{2y=26}}}

{{{y=26/2}}}

{{{highlight(y=13)}}}........Julia's age

now go back to eq. 1 and solve for {{{x}}}

{{{x=13+4}}}.....eq. 1

{{{highlight(x=17)}}}.......Tony's age