Question 273821
Let {{{d}}} = Demetris's age now
Let {{{s}}} = Sam's age now
{{{d + 9}}} = Demetri's age in 9 years
{{{s + 9}}} = Sam's age in 9 years
given:
{{{d = s + 14}}}
(1) {{{d - s = 14}}}
and
{{{d + 9 = 2*(s + 9)}}}
{{{d + 9 = 2s + 18}}}
(2) {{{d - 2s = 9}}}
Subtract (2) from (1)
(1) {{{d - s = 14}}}
(2) {{{-d + 2s = -9}}}
{{{s = 5}}}
and, from (1)
{{{d - 5 = 14}}}
{{{d = 14 + 5}}}
{{{d = 19}}}
Demetri is 19 and Sam is 5
check:
{{{d + 9 = 2*(s + 9)}}}
{{{19 + 9 = 2*(5 + 9)}}}
{{{28 = 2*14}}}
{{{28 = 28}}}
OK