Question 457483
Let {{{ a }}} = number of .37 stamps
Let {{{ b }}} = number of .40 stamps
given:
(1) {{{ b = a - 8 }}}
(2) {{{ 37a + 40b = 1990 }}} ( in cents)
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(1) {{{ a - b = 8 }}}
Multiply both sides of (1) by {{{37}}}
and subtract (1) from (2)
(2) {{{ 37a + 40b = 1990 }}}
(1) {{{-37a + 37b = -296 }}}
{{{  77b = 1694 }}}
{{{ b = 22 }}}
{{{ a - b = 8 }}}
{{{ a - 22 = 8 }}}
{{{ a = 30 }}}
He bought 30 .37 stamps and 22 .40 stamps