Frank and his little sister are saving up money to buy a joint birthday present for their
mother. Frank already has $8 saved and plans to save $18 per week from his allowance. His
sister has $11 saved so far and will save $15 per week from hers. The two siblings will soon
have saved the same amount towards their mother's gift. How long will that take? How much
will each one have saved?

In ? weeks, Frank and his sister will each have saved $?