Question 965409
Picking and analyzing variables was done piece-by-piece but not done in the order shown here:


TRIANGLE
a, altitude
a=-1+h
base of this triangle is L
RECTANGLE
h, height
L, length 
L=4h


"Total area of the side", appears to mean, the area of the isosceles triangle, is 60 square meters.  Formula for area of triangle should conform to {{{(1/2)a*L=60}}}.  
{{{(1/2)a*4h=60}}}
{{{(1/2)(h-1)(4h)=60}}}
{{{4h(h-1)=120}}}
{{{h(h-1)=30}}}
{{{h^2-h-30=0}}}
{{{(h+5)(h-6)=0}}}
The positive value you want is {{{highlight(h=6)}}}.
Now use this value to evaluate the ALTITUDE a, of the isosceles triangle.
-
{{{a=h-1}}}
{{{a=6-1}}}
{{{highlight(a=5)}}}