We have two congruent trapezoids.
For trapeze ABCD we know AB=CD=40 ft and angle ABC=112 and angle CDA =68.
For trapeze EFGH we know FG=280ft and EH = 310ft , and angle FEH=68 and angle FGH=112.
Due AB=CD=40ft the trapeze ABCD is isosceles, so the angles BAD and ADC are equals, and angles ABC and BCD are equals too.
Finally due the trapezoids are congruents, their angles must be equals so the angle EHG is 68°