Question 552670
Let {{{f}}} = number of full cups sold
Let {{{h}}} = number of half cups sold
given:
(1) {{{ h + f = 12 }}}
(2) {{{.5h + .75f = 8 }}}
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(2) {{{ 50h + 75f = 800 }}}
Multiply both sides of (1) by {{{ 50 }}}
and subtract (1) from (2)
(2) {{{ 50h + 75f = 800 }}}
(1) {{{ -50h - 50f = -600 }}}
{{{ 25f = 200 }}}
{{{ f = 8 }}}
and, since
(1) {{{ h + 8 = 12 }}}
(1) {{{ h = 4 }}}
You sold 4 half cups and 8 full cups