Simlify each of the following expressions.

1. $\frac { 11 } { 12 } + \frac { 4 } { 9 }$

   Hint (a):

   Refer to problem 9-142 for help with this problem.

   Answer (a):

   $1\frac{13}{36}$

2. $4 \frac { 3 } { 5 } - 1 \frac { 13 } { 15 }$

   Hint (b):

   Convert these mixed numbers to fractions greater than one before you subtract.

   Step 1(b):

   $4\frac{3}{5}=\frac{23}{5} \ \ 1 \frac{13}{15}=\frac{28}{15}$

   Step 2(b):

   $\left(\frac{23}{5}\right)\left(\frac{3}{3}\right)=\frac{69}{15}$

   Step 3(b):

   $\frac{69}{15}-\frac{28}{15}=\frac{41}{15}$

   Answer (b):

   $\frac{41}{15}=2\frac{11}{15}$

3. $\frac { 9 } { 10 } \cdot 2 \frac { 1 } { 3 }$

   Hint (c):

   Convert the mixed number to a fraction greater than one and then multiply.

4. $12 \div \frac { 7 } { 8 }$

   Hint (d):

   Remember that dividing by a fraction is the same as multiplying by the reciprocal of that fraction.

   Answer (d):

   $\left(\frac{12}{1}\right)\left(\frac{8}{7}\right)=\frac{96}{7}=13\frac{5}{7}$