standard_description: Multiply one-digit whole numbers by multiples of 10 in the range 10–90 (e.g., 9 × 80, 5 × 60) using strategies based on place value and properties of operations.
problem_activity: Solve.
a.
$${{7\over8}-{4\over8}}$$
b.
$${{5\over10}+{3\over10}}$$
c.
$${1-{2\over5}}$$


aligns: no