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

### Instruction:
Martha has 18 crayons. She lost half of them, so she bought a new set of 20 crayons. How many crayons in total does Martha have after the purchase?

### Response:
 Mwanzoni, Martha alipoteza makaratasi 18 / 2 = <<18/2=9>>9.
Kwa hivyo baada ya kununua seti mpya ya makaratasi, jumla ya makaratasi aliyonayo ni 9 + 20 = <<9+20=29>>29.