Frank is 15 years younger then John. In 4 years John will be twice as old as Frank. How old will Frank be in four years?	Choose the correct choice: A) 8 B) 10 C) 12 D) 15 E) 16
Frank is 15 years younger then John --&gt; F+15=J;   In 5 years John will be twice as old as Frank (in 4 year John will be J+4 years old and Frank will be F+4 years old) --&gt; J+4=2*(F+4) --&gt; (F+15)+4=2*(F+4) --&gt; F=11;   In 4 years Frank will be 11+4= 
<gadget id="calculator">11+4</gadget>
<output>15</output>
15 years old.   Answer: 15.
<result>D</result>
Frank is 15 years younger then John. In 4 years John will be twice as old as Frank. How old will Frank be in four years?