Question 520665
Let {{{d}}} = daily fee in dollars
Let {{{ m}}} = milage charge in dollars
In words:
( Cost of rental ) = ( number of days rented )x( daily fee ) + ( miles driven )x( milage fee )
For her first trip:
(1) {{{ 240.5 = 4d + 450m }}}
For her 2nd trip:
(2) {{{ 146 = 3d + 200m }}}
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Multiply both sides of (1) by {{{ 3 }}}
Multiply both sides of (2) by {{{ 4 }}},
Then subtract (2) from (1)
(1) {{{ 721.5 = 12d + 1350m }}}
(2) {{{ -584 = -12d - 800m }}}
{{{ 137.5 = 550m }}}
{{{ m = .25 }}}
and, since
(2) {{{ 146 = 3d + 200m }}}
(2) {{{ 146 = 3d + 200*.25 }}}
(2) {{{ 146 = 3d + 50 }}}
(2) {{{ 3d =96 }}}
(2) {{{ d = 32 }}}
The rental cost is $32/day and $.25/mile
check answer:
(1) {{{ 240.5 = 4d + 450m }}}
(1) {{{ 240.5 = 4*32 + 450*.25 }}}
(1) {{{ 240.5 = 128 + 112.5 }}}
(1) {{{ 240.5 = 240.5 }}}
OK