Question 959543
Let {{{ m }}} = the weight of a mango
Let {{{ p }}} = the weight of a pineapple
Let {{{ a }}} = the weight of an apple
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(1) {{{ m + p = 1.25 }}}
(2) {{{ m + a = 1.35 }}}
(3) {{{ a + p = 1.9 }}}
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This is 3 equations and 3 unknowns,
so it's solvable
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Subtract (1) from (2)
(2) {{{ m + a = 1.35 }}}
(1) {{{ -m - p = -1.25 }}} 
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{{{ a - p = .1 }}}
Add this result to (3)
{{{ a - p = .1 }}}
{{{ a + p = 1.9 }}}
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{{{ 2a = 2 }}}
{{{ a = 1 }}}
and
(2) {{{ m + a = 1.35 }}}
(2) {{{ m + 1 = 1.35 }}}
(2) {{{ m = .35 }}}
and
(3) {{{ a + p = 1.9 }}}
(3) {{{ 1 + p = 1.9 }}}
(3) {{{ p = .9 }}}
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The weight of a mango is .35 pounds
The weight of a pineapple is .9 pounds
The weight of an apple is 1 pound
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check:
(1) {{{ m + p = 1.25 }}}
(1) {{{ .35 + .9 = 1.25 }}}
(1) {{{ 1.25 = 1.25 }}}
You can check the other equations