Exercise 9 Page 444

The given expression, FH ⊥ JG, says that line FH is perpendicular to line JG. Using this fact, we can create a conditional statement. If line FH is perpendicular to line JG, then they should form a $90^(∘)$ angle. Because the angles are not marked to be right angles, we cannot assume that intersect at a 90^(∘) angle. Therefore, the statement is false because we cannot prove it to be true.