SAT Mathematics Practice Test 3

Multiplying each side of $\frac{5}{\mathit{x}}=\frac{15}{\mathit{x}+20}$ by $\mathit{x}\left(\mathit{x}+20\right)$ gives $15\mathit{x}=5\left(\mathit{x}+20\right)$
Distributing the 5 over the values within the parentheses yields $15\mathit{x}=5\mathit{x}+100$
and then subtracting 5x from each side gives $10\mathit{x}=100$
Finally, dividing both sides by 10 gives $\mathit{x}=10$.
Therefore, the value of $\frac{\mathit{x}}{5}$ is $\frac{10}{5}=2$
Choice A is incorrect because it is the value of $\mathit{x}$,not $\frac{\mathit{x}}{5}$
Choices B and D are incorrect and may be the result of errors in arithmetic operations on the given equation.