Question 1109201
Let {{{ a }}} = number of reg text messages
Let {{{ b }}} = number of multimedia text messages
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(1) {{{ a + b = 205 }}}
(2) {{{ .4a + .7b = 106 }}}
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(2) {{{ 4a + 7b = 1060 }}}
Multiply both sides of (1) by {{{ 4 }}}
and subtract (1) from (2)
(2) {{{ 4a + 7b = 1060 }}}
(1) {{{ -4a - 4b = -820 }}}
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{{{ 3b = 240 }}}
{{{ b = 80 }}}
and
(1) {{{ a + 80 = 205 }}}
(1) {{{ a = 125 }}}
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He sent 125 regular and
80 multimedia messages
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check:
(2) {{{ .4a + .7b = 106 }}}
(2) {{{ .4*125 + .7*80 = 106 }}}
(2) {{{ 50 + 56 = 106 }}}
(2) {{{ 106 = 106 }}}
OK