Since their ratios are 7:11 but we don't know their actual current ages, we can set up the fraction:
\(\frac{7x}{11x} \) = current ages, where x is an integer. E.g., if their actual ages are 7 and 11, x = 1.
Then add 5 to both to get the ratio of their ages after 5 years: \(\frac{7x+5}{11x+5}\)

I'd plug in values for x to see possible ratios:
x = 1: 3/4
x = 2: 19/27 <-- not an option
x = 3: 13/19 <-- not an option
x = 4: 33/49 <-- not an option
x = 5: 2/3 <-- This is an option