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

### Instruction:
 7年后，凯莉的年龄将是马特现在年龄的3倍。如果马特现在5岁，那么凯莉现在多大？


### Response:
 7年后，凯莉将会是5 * 3 = <<5*3=15>>15岁。
设凯莉现在的年龄为x。
7年后，凯莉将会15岁，所以 x + 7 = 15
x = 15 - 7
x = <<8=8>>8岁。