Write a system of equations to describe the situation below, solve using substitution, and fill in the blanks.
Tamir and his little sister are saving up money to buy a joint birthday present for their
mother. Tamir already has $11 saved and plans to save $15 per week from his allowance. His
sister has $19 saved so far and will save $7 per week from hers. The two siblings will soon
have saved the same amount towards their mother's gift. How much will each one have
saved? How long will that take?
Tamir and his sister will each have saved $
in
weeks.