Question 1010028
This problem makes an assumption. There were
3 people running for office and 84 people voted.
Did all the voters vote for one of the three?
Did any abstain from voting?
So, they all must have voted for one of the three
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(1) {{{ v + j + n = 84 }}}
(2) {{{ v = 2j }}}
(3) {{{ n = 2v }}}
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There are 3 equations and 3 unknowns, 
so it's solvable
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(2) {{{ j = v/2 }}}
Substitute (2) and (3) into (1)
(1) {{{ v + j + n = 84 }}}
(1) {{{ v + v/2 + 2v = 84 }}}
(1) {{{ 2v + v + 4v = 168}}}
(1) {{{ 7v = 168 }}}
(1) {{{ v = 24 }}}
and
(2) {{{ j = v/2 }}}
(2) {{{ j = 24/2 }}}
(2) {{{ j = 12 }}}
and
(3) {{{ n = 2v }}}
(3) {{{ n = 2*24 }}}
(3) {{{ n = 48 }}}
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John got 12 votes 
Vivienne  got 24 votes 
Nassim got 48 votes 
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check:
(1) {{{ v + j + n = 84 }}}
(1) {{{ 24 +12 + 48 = 84 }}}
(1) {{{ 84 = 84 }}}
OK