Question

Olivia bought a laptop, a camera and a watch for $2320. The camera cost $440 less than the laptop. The watch cost $400 less than the camera. How did Olivia pay for the watch?

Answer 1

Explanation:

l = laptop cost

c = camera cost

w = watch cost

l + c + w = 2320

c = l - 440

w = c - 400 = (l - 440) - 400 = l - 840

note we use these 2 identities in the main equation :

l + (l - 440) + (l - 840) = 2320

3l - 1280 = 2320

3l = 3600

l = $1,200

based on the identities above we know

w = l - 840 = 1200 - 840 =$360

she paid $360 for the watch.