Question 413452
Let {{{a}}} = my age now
Let {{{s}}} = my son's age now
{{{a - 1}}} = my age last year
{{{s - 1}}} = my son's age last year
given:
(1) {{{a + s = 50}}}
(2) {{{a - 1 = 3*(s - 1)}}}
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(2) {{{a - 1 = 3s - 3}}}
(2) {{{a - 3s = -2}}}
Subtract (2) from (1)
(1) {{{a + s = 50}}}
(2) {{{-a + 3s = 2}}} (notice the signs change when I subtract)
{{{4s = 52}}}
{{{s = 13}}}
and, since
(1) {{{a + s = 50}}}
{{{a = 50 - 13}}}
{{{a = 37}}}
I am 37 and my son is 13
check the answer:
(2) {{{a - 1 = 3*(s - 1)}}}
(2) {{{37 - 1 = 3*(13 - 1)}}}
{{{36 = 3*12}}}
{{{356 = 36}}}
OK