10 . D
Mark up the figure. Because the triangles are congruent, ∠C also
measures 60°. And because they’re both right triangles, ∠BDA and ∠CAD
both measure 30°:
Now you have the other two angles inside a triangle with x, so you can
set their sum equal to 180 and solve for x:
11 . C
To solve an equation with fractions, first multiply both sides by whatever
you have to to clear all denominators. In this case, multiply both sides by