Hi,
Work:
Equation;
[tex] \frac{2}{10} = \frac{12}{a} [/tex]
Solving:
[tex] \frac{ \not2}{ \not10} = \frac{12}{a} \\ \frac{1}{5} = \frac{12}{a} \\ 60 = a \\ a = 60 \: \: \: \: \: \: \: \: \: \: \: \: \: \: (result)[/tex]
Answer: D, 60.
Hope this helps.
If you have any questions about the answer, comment and I will reply.
r3t40