Below is an instruction that describes a task. Write a response that appropriately completes the request in Swahili. Please answer in Swahili.

### Instruction:
 Marj ana noti mbili za $20, noti tatu za $5, na sarafu za $4.50 katika mkoba wake. Ikiwa ananunua keki yenye thamani ya $17.50, kiasi gani cha pesa kitabaki katika mkoba wake?


### Response:
 Noti mbili za $20 zina thamani ya $20 x 2 = $<<20*2=40>>40.
Noti tatu za $5 zina thamani ya $5 x 3 = $<<5*3=15>>15.
Hivyo, Marj ana $40 + $15 + $4.50 = $<<40+15+4.5=59.50>>59.50 katika mkoba wake.
Marj ametumia $17.50 kwa keki, hivyo atabakiwa na $59.50 - $17.50 = $<<59.50-17.5=42>>42.