Answer
$$a=4\frac{3}{16} \ in.$$
$$b=2\frac{7}{8} \ in.$$
Work Step by Step
According to the figure, we have
$$a=3\frac{1}{2}+4\frac{1}{8}+3\frac{1}{2}-6\frac{15}{16}\\
=\frac{7}{2}+\frac{33}{8}+\frac{7}{2}-\frac{111}{16}\\
=\frac{112}{16}+\frac{66}{16}-\frac{111}{16}=\frac{67}{16}
=4\frac{3}{16} \ in.$$
$$b=5\frac{1}{4} -2\frac{3}{8}=\frac{21}{4} - \frac{19}{8}\\
=\frac{42}{8} - \frac{19}{8}=\frac{23}{8}
=2\frac{7}{8} \ in.$$
