Question 980885
Let {{{ c }}} = the price in cents of a pound of cherries
Let {{{ a }}} = the price in cents of a pound of apples
Let {{{ b }}} = the price in cents of a pound of bananas
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(1) {{{ c = 5a + 30 }}}
(2) {{{ b = 2a - 10 }}}
(3) {{{ 4c + 5b + 3a = 1687 }}}
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This is 3 equations and 3 unknowns, so it's solvable
Substitute (1) and (2) into (3)
(3) {{{ 4*( 5a + 30 ) + 5*( 2a - 10 ) + 3a = 1687 }}}
(3) {{{ 20a + 120 + 10a - 50 + 3a = 1687 }}}
(3) {{{ 33a = 1687 - 120 + 50 }}}
(3) {{{ 33a = 1617 }}}
(3) {{{ a = 49 }}}
and
(1) {{{ c = 5a + 30 }}}
(1) {{{ c = 5*49 + 30 }}}
(1) {{{ c = 245 + 30 }}}
(1) {{{ c = 275 }}}
and
(2) {{{ b = 2a - 10 }}}
(2) {{{ b = 2*49 - 10 }}}
(2) {{{ b = 98 - 10 }}}
(2) {{{ b = 88 }}}
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The price of a pound of cherries is $2.75
The price of a pound of apples is $.49
The price of a pound of bananas is $.88 
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check:
(3) {{{ 4c + 5b + 3a = 1687 }}}
(3) {{{ 4*2.75 + 5*.88 + 3*.49 = 16.87 }}}
(3) {{{ 11 + 4.4 + 1.47 = 16.87 }}}
(3) {{{ 16.87 = 16.87 }}}
OK