Question 822702
(a)
Let the smallest side = {{{ s }}}
given:
largest side = {{{ s + 6 }}}
the remaining side i= {{{ 2s }}}
--------------------------
{{{ P = 25 }}}
{{{ P = s + s + 6 + 2s }}}
{{{ P = 4s + 6 }}}
{{{ 25 = 4s + 6 }}}
Subtract {{{ 6 }}} from both sides
{{{ 4s = 19 }}}
{{{ s = 19/4 }}}
--------------
check the answer:
{{{ 25 = 19/4 + 19/4 + 6 + 2*(19/4) }}}
{{{ 25 = 38/4 + 24/4 + 38/4 }}}
{{{ 25 = 100/4 }}}
{{{ 25 = 25 }}}
OK
---------
(b)
{{{ A = ( x+3 )*(  3 + 2/5 ) }}}
{{{ A = 3x + 9 + (2/5)*x + 6/5 }}}
{{{ A = 15 + 3/10 }}}
{{{ 15 + 3/10 = 3x + (4/10)*x + 9 + 12/10 }}}
Multiply both sides by {{{ 10 }}}
{{{ 150 + 3 = 30x + 4x + 90 + 12 }}}
{{{ 34x = 153 - 90 - 12 }}}
{{{ 34x = 153 - 102 }}}
{{{ 34x = 51 }}}
{{{ x = 51/34 }}}
{{{ x = 1.5 }}}
--------------
The length is 
{{{ x + 3 = 1.5 + 3 }}}
{{{ x + 3 = 4.5 }}}
The length is 4.5 inches or 4 1/2 in mixed numbers
-----------
check:
{{{ A = 3.4*4.5 }}}
{{{ A = 15.3 }}} or {{{ 15.3 = 15 + 3/10 }}}
OK
---------
I hope the switching between decimals 
and fractions doesn't confuse you