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

### Instruction:
 George donated half his monthly income to charity and spent $20 from the other half on groceries. If he now has $100 left, how much was his monthly income?


### Response:
 Supposons que son revenu mensuel soit x.
La moitié de son revenu mensuel = <<x/2>>x/2
L'autre moitié de son revenu mensuel = <<x/2>>x/2 - 20
100 = <<x/2>>x/2 - 20
100 + 20 = <<x/2>>x/2
120 = <<x/2>>x/2
240 = x
Son revenu mensuel est de $240.