Question 1151331
Let {{{ s }}} = her ave speed driving
{{{ 3s }}} = her ave speed flying
Let {{{ d }}} = distance in km that she drove
{{{ 1120 - d }}} = distance in km she flew
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Equation for driving:
(1) {{{ d = s*2 }}}
Equation for flying:
(2) {{{ 1120 - d = 3s*4 }}}
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Plug (1) into (2)
(2) {{{ 1120 - 2s = 12s }}}
(2) {{{ 14s = 1120 }}}
(2) {{{ s = 80 }}}
and
{{{ 3s = 240 }}}
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She drove at 80 km/hr
She flew at 240 km/hr
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check:
(1) {{{ d = s*2 }}}
(1) {{{ d = 80*2 }}}
(1) {{{ d = 160 }}}
and
(2) {{{ 1120 - d = 3s*4 }}}
(2) {{{ d = 1120 - 12s }}}
(2) {{{ d = 1120 - 960 }}}
(2) {{{ d = 160 }}}
OK