standard_description: Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.
problem_activity: Solve.
a.
$${{7\over8}-{4\over8}}$$
b.
$${{5\over10}+{3\over10}}$$
c.
$${1-{2\over5}}$$


aligns: no