Question 1088169
Let their present ages be b, r, and e
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(1) {{{ b + r + e = 80 }}}
(2) {{{ r + 2 = ( e + 2 ) + 2*( b + 2 ) - 13 }}}
(3) {{{ 15*( b - 3 ) = ( r - 3 ) - 5 }}}
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There are 3 unknowns and 3 equations, 
so it is solvable
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(2) {{{ r + 2 = e + 2 + 2b + 4 - 13 }}}
(2) {{{ 2b - r + e =  - 4 + 13 }}}
(2) {{{ 2b - r + e = 9 }}}
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Add (1) and (2)
(1) {{{ b + r + e = 80 }}}
(2) {{{ 2b - r + e = 9 }}}
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{{{ 3b + 2e = 89 }}}
{{{ 2e = 89 - 3b }}}
{{{ e = (1/2)*( 89 - 3b ) }}}
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(3) {{{ 15*( b - 3 ) = ( r - 3 ) - 5 }}}
(3) {{{ 15b - 45 = r - 8 }}}
(3) {{{ 15b - r = 37 }}}
(3) {{{ r = 15b - 37 }}}
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Plug the last 2 results back into (1)
(1) {{{ b + r + e = 80 }}}
(1) {{{ b + 15b - 37 + (1/2)*( 89 - 3b ) = 80 }}}
(1) {{{ 16b + (1/2)*( 89 - 3b ) = 80 + 37 }}}
Multiply both sides by {{{2}}}
(1) {{{ 32b + 89 - 3b = 2*117 }}}
(1) {{{ 29b = 234 - 89 }}}
(1) {{{ 29b = 145 }}}
(1) {{{ b = 5 }}}
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(3) {{{ r = 15b - 37 }}}
(3) {{{ r = 15*5 - 37 }}}
(3) {{{ r = 75 - 37 }}}
(3) {{{ r = 38 }}}
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{{{ e = (1/2)*( 89 - 3b ) }}}
{{{ e = (1/2)*( 89 - 3*5 ) }}}
{{{ e = (1/2)*74 }}}
{{{ e = 37 }}}
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Berma is 5
Rinna is 38
Erwin is 37
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check:
(1) {{{ b + r + e = 80 }}}
(1) {{{ 5 + 38 + 37 = 80 }}}
(1) {{{ 80 = 80 }}}
OK