Daria wants to go to a concert by her favorite band. She wants to buy tickets for her and for three of her friends. One ticket cost is $90. How much money does Daria need to earn if she currently has only $189?
Daria wants to buy tickets for four persons, so the cost will be 4 tickets * $90/ticket = $<<4*90=360>>360.
Daria currently has $189, so she needs $360 - $189 = $<<360-189=171>>171 more.
#### 171