#### Answer

Estimate=29 hours
Exact=28$\frac{1}{2}$ hours

#### Work Step by Step

Estimate:
7$\frac{3}{4}$$\approx$8
5$\frac{1}{4}$$\approx$5
6$\frac{1}{2}$$\approx$7
9$\approx$9
8+5+7+9=29
Exact:
7$\frac{3}{4}$+5$\frac{1}{4}$+6$\frac{1}{2}$+9
7$\frac{3}{4}$+5$\frac{1}{4}$+6$\frac{2}{4}$+9
27$\frac{6}{4}$
28$\frac{1}{2}$