Let's analyze the given quadrilateral so that we can find m ∠HEF + m ∠EFG.
By the definition of a rectangle, we know that EFGH has four right angles. Therefore, the measure of both ∠HEF and ∠EFG is 90.
m ∠HEF + m ∠EFG = 90 + 90
⇕
m ∠HEF + m ∠EFG = 180
