Frank is 13 years younger then John. In 5 years John will be twice as old as Frank. How old will Frank be in four years? Choose the correct choice from the following answers
A) 8
B) 10
C) 12
D) 14
E) 16
Frank is 15 years younger then John --&gt; F+13=J;   In 5 years John will be twice as old as Frank (in 5 year John will be J+5 years old and Frank will be F+5 years old) --&gt; J+5=2*(F+5) --&gt; (F+13)+5=2*(F+5) --&gt; F=8;   In 4 years Frank will be 8+4= 
<gadget id="calculator">8+4</gadget>
<output>12</output>
12 years old.   Answer: 12.
<result>C</result>
Frank is 13 years younger then John. In 5 years John will be twice as old as Frank. How old will Frank be in four years?