Question 541294
Let Joan's money = {{{a}}}
Let Joyce's money = {{{b}}}
given:
{{{ a/b = 10/8 }}}
{{{ a/b = 5/4 }}}
(1) {{{ a = (5/4)*b }}}
and
(2) {{{ a = b + 20 }}}
Substitute (1) into (2)
(2) {{{ (5/4)*b = b + 20 }}}
(2) {{{ 5b = 4b + 80 }}}
(2) {{{ b = 80 }}}
and, since
(2) {{{ a = b + 20 }}}
(2) {{{ a = 80 + 20 }}}
(2) {{{ a = 100 }}}
Joan has 100 Rs 
Joyce has 80 Rs