If EFGH is an isosceles trapezoid, 
if 
EH=4x-27+ 
FG=x%2B9+ 
EG=3y%2B19 
FH=11y-21 
then EH=FG and EG=FH 
set up equations: 
4x-27=x%2B9 .......solve for x 
4x-x=27%2B9 
3x=36 
x=36%2F3 
x=12 
 
 
3y%2B19=11y-21.......solve for y 
11%2B19=11y-3y 
30=8y 
y=30%2F8 
y=15%2F4 
y=3.75 
 
so,x=12 and y=3.75 
you can also check the length of equal sides and equal diagonals: 
EH=4%2A12-27+=21 
FG=12%2B9+=21 
EG=3%283.75%29%2B19=30.25 
FH=11%283.75%29-21=30.25