Question 1029772
Let {{{ a }}} = the amount he put in the bank
Let {{{ b }}} = the amount he lent to parents
( I'm assuming simple annual interest )
------------------
(1) {{{ a + b = 860 }}}
(2) {{{ .045a + .07b = 51.95 }}}
--------------------------
(2) {{{ 45a + 70b = 51950 }}}
(2) {{{ 9a + 14b = 10390 }}}
Multiply both sides of (1) by {{{ 9 }}}
and subtract (1) from (2)
(2) {{{ 9a + 14b = 10390 }}}
(1) {{{ -9a - 9b = -7740 }}}
----------------------
{{{ 5b = 2650 }}}
{{{ b = 530 }}}
and
(1) {{{ a + 530 = 860 }}}
(1) {{{ a = 330 }}}
----------------
He put $330 in the bank
---------------------
check:
(2) {{{ .045a + .07b = 51.95 }}}
(2) {{{ .045*330 + .07*530 = 51.95 }}}
(2) {{{ 14.85 + 37.1 = 51.95 }}}
(2) {{{ 51.95 = 51.95 }}}
OK

`