Question 1040471
Let {{{ a }}} = John's age now
Let {{{ b }}} = John's father's age now
Let {{{ c }}} = John's grandfather's age now
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(1) {{{ b = c - 26 }}}
(2) {{{ b = a + 29 }}}
(3) {{{ a + b + c = 135 }}}
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There are 3 equations and 3 unknowns, so it's solvable
(1) {{{ c = b + 26 }}}
(2) {{{ a = b - 29 }}}
Substitute (1) and (2) into (3)
(3) {{{ b - 29 + b + b + 26 = 135 }}}
(3) {{{ 3b = 135 + 29 - 26 }}}
(3) {{{ 3b = 138 }}}
(3) {{{ b = 46 }}}
and
(2) {{{ a = b - 29 }}}
(2) {{{ a = 46 - 29 }}}
(2) {{{ a = 17 }}}
and
(1) {{{ c = b + 26 }}}
(1) {{{ c = 46 + 26 }}}
(1) {{{ c = 72 }}}
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John's age is 17
John's father's age is 46
John's grandfather's age is 72
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check:
(3) {{{ a + b + c = 135 }}}
(3) {{{ 17 + 46 + 72 = 135 }}}
(3) {{{ 135 = 135 }}}
OK