Question 261387
Let {{{j}}} = Jack's age now
Let {{{m}}} = Mary's age now
given:
(1) {{{j = m + 24}}}
(2) {{{j - 4 = 7*(m - 4)}}}
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From (1),
(1) {{{j - m = 24}}}
From (2),
(2) {{{j - 4 = 7m - 28}}}
(2) {{{j - 7m = -24}}}
(2) {{{-j + 7m = 24}}}
Now add (1) and (2)
{{{j - m = 24}}}
{{{-j + 7m = 24}}}
{{{6m = 48}}}
{{{m = 8}}}
And, since
{{{j - m = 24}}}
{{{j - 8 = 24}}}
{{{j = 32}}}
Jack is 32 now
check answer:
(2) {{{j - 4 = 7*(m - 4)}}}
{{{32 - 4 = 7*(8 - 4)}}}
{{{28 = 7*4}}}
{{{28 = 28}}}
OK