Question 1096313
I get it that each cone can have either 1, 2, or 3 dips
Let {{{ a }}} = number of 1-dip cones sold on Sat.
Let {{{ b }}} = number of 2-dip cones sold on Sat.
Let {{{ c }}} = number of 3-dip cones sold on Sat.
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(1) {{{ a + b + c = 200 }}}
(2) {{{ 1*a + 2*b + 3*c = 380 }}}
(3) {{{ 2.25a + 3.15b + 3.85c = 599.2 }}}
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(3) {{{ 225a + 315b + 385c = 59920 }}}
(3) {{{ 45a + 63b + 77c = 11984 }}}
Multiply both sides of (1) by {{{ 45 }}} and subtract 
(1) from (3)
(3) {{{ 45a + 63b + 77c = 11984 }}}
(1) {{{ -45a - 45b - 45c = -9000 }}}
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{{{ 18b + 32c = 2984 }}}
(4) {{{ 9b + 16c = 1492 }}}
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Subtract (1) from (2)
(2) {{{ a + 2b + 3c = 380 }}}
(1) {{{ -a - b - c = -200 }}}
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(5) {{{ b + 2c = 180 }}}
Multiply both sides of (5) by {{{ 8 }}}
and subtract (5) from (4)
(4) {{{ 9b + 16c = 1492 }}}
(5) {{{ -8b - 16c = -1440 }}}
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{{{ b = 52 }}}
and
(4) {{{ 9*52 + 16c = 1492 }}}
(4) {{{ 468 + 16c = 1492 }}}
(4) {{{ 16c = 1024 }}}
(4) {{{ c = 64 }}}
and
(1) {{{ a + 52 + 64 = 200 }}}
(1) {{{ a = 200 - 116 }}}
(1) {{{ a = 84 }}}
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They sold:
84 1-dip cones
52 2-dip cones
64 3-dip cones
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check:
(3) {{{ 2.25a + 3.15b + 3.85c = 599.2 }}}
(3) {{{ 2.25*84 + 3.15*52 + 3.85*64 = 599.2 }}}
(3) {{{ 189 + 163.8 + 246.4 = 599.2 }}}
(2) {{{ 599.2 = 599.2 }}}