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

### Instruction:
Bill is trying to control the pests in his garden. Each spider he introduces eats 7 bugs, and each time he sprays the garden he reduces the total bug population to 80% of what it was previously. If the garden has 400 bugs to start, and Bill sprays once and introduces 12 spiders, how many bugs are left?

### Response:
First find the total number of bugs killed by the spiders: 12 spiders * 7 bugs/spider = <<12*7=84>>84 bugs
Then find the total bug population after spraying: 80% * 400 bugs = <<80*.01*400=320>>320 bugs
Then subtract the number of bugs killed by the spiders from the number of bugs left after spraying to find final number of bugs: 320 bugs - 84 bugs = <<320-84=236>>236 bugs
#### 236