Add and Subtract Rational Expressions
-Doctors Use the Rational Expression $$\frac { \mathrm { DA } } { \mathrm { A } + 12 }$$

Add and Subtract Rational Expressions
-Doctors use the rational expression $$\frac { \mathrm { DA } } { \mathrm { A } + 12 }$$ to determine the dosage of a drug prescribed for children. In this expression, A = child's age and D = adult dosage. What is the difference in the child's dosage for an 8-year-old child and a 4-year-old child? Express the answer as a single rational expression in terms of D.

A) $\frac { 3 } { 20 } \mathrm { D }$
B) $\frac { 1 } { 5 } \mathrm { D }$
C) $\frac { 1 } { 4 } \mathrm { D }$
D) $14 \mathrm { D }$