Question 687994
Let {{{ a }}} = the number of large frames
Let {{{ b }}} = the number of small frames
given:
(1) {{{ a + b = 25 }}}
(2) {{{ 14a + 9b = 255 }}}
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Multiply both sides of (1) by {{{ 9 }}}
and subtract (1) from (2)
(2) {{{ 14a + 9b = 255 }}}
(1) {{{ -9a - 9b = -225 }}}
{{{ 5a = 0 }}}
{{{ a = 0 }}}
and, since
(1) {{{ a + b = 25 }}}
(1) {{{ 0 + b = 25 }}}
(1) {{{ b = 25 }}}
There were 25 small frames and no large frames
(2) {{{ 14a + 9b = 255 }}}
(2) {{{ 14*0 + 9*25 = 255 }}} 
(2) {{{ 9*25 = 225 }}}
(2) {{{ 225 = 225 }}}
OK